@article { ISI:000340526400001, title = {Stable silanone with a three-coordinate silicon atom: a century-long wait is over}, journal = {Angewandte Chemie-International Edition}, volume = {53}, number = {34}, year = {2014}, month = {AUG}, pages = {8820-8822}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, keywords = {cations, germanones, Ketones, silanones, transition metals}, issn = {1433-7851}, doi = {10.1002/anie.201404793}, author = {Sen, Sakya S.} } @article { ISI:000358022300001, title = {Cations and dications of heavier group 14 elements in low oxidation states}, journal = {Dalton Transactions}, volume = {44}, number = {29}, year = {2015}, month = {JUN}, pages = {12903-12923}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Cations and dications of heavier group 14 elements in their low oxidation state have received widespread attention in recent years. The journey started with the isolation of a series of cations of the composition [(C5Me5)E:](+) [E = Si-Pb], followed by the more recent isolation of a Ge(II) dication encapsulated within a cryptand, a carbodiphosphorane stabilized [GeCl](+) monocation with a two coordinate Ge atom, Si(II) cations and dications stabilized by N-heterocyclic carbenes (NHCs), which highlights the ongoing growth and interest in the chemistry of tetrel(II) cations. This is presumably because the central atom (E) in these compounds contains two or three unoccupied valence orbitals as well as holds a lone pair of electrons. Such an electronic description represents ambiphilicity, which is of great interest for catalysis. The successful synthesis of divalent group 14 cations requires new synthetic strategies based on the sterically demanding neutral or monoanionic ligands, utilization of counter anions, and solvents with low nucleophilicity in order to minimize the degree of interactions with the cations. An alternative approach for the realization of divalent cations of group 14 elements is their coordination to the transition metals. This synthetic approach was successfully applied for the isolation of a range of transition metal coordinated divalent cations of group 14 elements. Apart from arousing academic interest some of these cations have found application as activators in the Ziegler-Natta polymerization of alkenes.

}, issn = {1477-9226}, doi = {10.1039/c5dt01912e}, author = {Swamy, V. S. V. S. N. and Pal, Shiv and Khan, Shabana and Sen, Sakya S.} } @article { ISI:000345901600049, title = {Stepwise isolation of low-valent, low-coordinate Sn and Pb mono- and dications in the coordination sphere of platinum}, journal = {Chemical Science}, volume = {6}, number = {1}, year = {2015}, month = {OCT}, pages = {425-435}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Synthetic access to low-coordinate Pb mono- and dications is in general impeded due to their poor solubility and highly electrophilic nature. However, the electrophilicity of these cations can be tamed by attaching them to electron-rich transition metals. Following this principle we have isolated low-valent Pb mono- ([(Cy3P)(2)Pt-PbCl](2)[AlCl4](2), 8a) and dications ([(Cy3P)(2)Pt(Pb)][AlCl4](2), 11) in the coordination sphere of platinum. The same approach then has been implemented for the isolation of analogous low-valent Sn mono- (7a) and dications (10). An energy decomposition analysis (EDA-NOCV) was performed to investigate the nature of Pt-Pb and Pb-Cl bonding in [(Cy3P)(2)Pt(PbCl2)] (2), 8a and 11. The results show that the Pt-Pb bonds in 8a and 11 are electron-sharing in nature, whereas that of the precursor 2 is a dative bond. The breakdown of attractive interactions in 2, 8a and 11 reveals that the ionic interactions in the analyzed Pt-Pb and Pb-Cl bonds are always stronger than the covalent interactions, except for the Pb-Cl bond in 8a. The calculated D3 dispersion energies show that dispersion interactions play a key role in the thermodynamic stability of 2, 8a and 11.

}, issn = {2041-6520}, doi = {10.1039/c4sc02948h}, author = {Braunschweig, Holger and Celik, Mehmet Ali and Dewhurst, Rian D. and Heid, Magdalena and Hupp, Florian and Sen, Sakya S.} } @article {43051, title = {Benz{\textendash}amidinato stabilized a monomeric calcium Iodide and a lithium calciate(II) cluster featuring group 1 and group 2 elements}, journal = {ChemistrySelect}, volume = {1}, year = {2016}, month = {APR}, pages = {1066{\textendash}1071}, abstract = {

Soluble calcium halides reported so far are mostly dimeric in nature. The halides occupy the bridging position and thus provide additional coordination to the metal. We obtained a monomeric calcium iodide [{PhC(NiPr)(2)} CaI(thf)(3)] (1) from the reaction of [PhC(NiPr)(2)] Li with Cal(2) in THF. The compound has been stabilized by electronic donation and steric shielding from the amidinate ligand as well as coordination of three THF molecules. 1 does not show any propensity towards ligand exchange reaction. When the same reaction is carried out in diethyl ether instead of THF, it led to the formation of a Li calciate(II) cluster of composition L2Ca4I8Li4O (L= PhC(NiPr)(2)) (2) with an encapsulated O2+ in the middle of a tetrahedron spanned by four Ca2+ ions. 2 represents a metal-rich halide comprising of both alkali and alkaline earth metals which is quite unprecedented. Another notable aspect is that the amidinate ligand binds to the calcium atom in chelating bidentate mode in 1, whereas in 2 each N atom of the amidinate ligands binds to two Ca atoms leading to bridging bis-chelating coordination mode.

}, doi = {10.1002/slct.201600285}, author = {Yadav, Sandeep and Swamy, V. S. V. S. N. and Gonnade, Rajesh G. and Sen, Sakya S.} } @article { ISI:000370029900002, title = {Compounds with low-valent p-block elements for small molecule activation and catalysis}, journal = {Chemcatchem}, volume = {8}, number = {3}, year = {2016}, month = {FEB}, pages = {486-501}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {

The past decade has witnessed staggering progress in the chemistry of compounds with low-valent main-group elements. Although these discoveries are mostly fundamental by nature, these compounds show promising reactivity towards small molecule activation. The reactivity of these compounds stems from the modest HOMO-LUMO energy gap; a characteristic known for the transition metals. The journey began in 2005 with the facile activation of dihydrogen by an alkyne analog of germanium [ArGeGeAr; Ar=2,6-Trip(2)-C6H3 (Trip=2,4,6-iPr(3)-C6H2)]. Subsequently, tremendous progress has been achieved in understanding and elucidating the potential of these compounds to activate small molecules as well as to use them in a variety of stoichiometric and catalytic transformations. In this review, we focus on developments in the activation of H-2, NH3, CO, and CO2 by compounds with multiply bound or open shell main-group elements. Emphasis will be given to their catalytic activity.

}, keywords = {activation, carbenes, main-group elements, silylenes, small molecules}, issn = {1867-3880}, doi = {10.1002/cctc.201501015}, author = {Yadav, Sandeep and Saha, Sumana and Sen, Sakya S.} } @article {43389, title = {Dynamic, reversible oxidative addition of highly polar bonds to a transition metal}, journal = {Journal of the American Chemical Society}, volume = {138}, year = {2016}, month = {DEC}, pages = {16140-16147}, abstract = {The combination of Pt complexes and indium trihalides leads to compounds that form equilibria in solution between their In X oxidative addition (OA) products (Pt indyl complexes) and their metal-only Lewis pair (MOLP) isomers (LnPt -> InX3). The position of the equilibria can be altered reversibly by changing the solvent, while the equilibria can be reversibly and irreversibly driven toward the MOLP products by addition of further donor ligands. The results mark the first observation of an equilibrium between MOLP and OA isomers, as well as the most polar bond ever observed to undergo reversible oxidative addition to a metal complex. In addition, we present the first structural characterization of MOLP and oxidative addition isomers of the same compound. The relative energies of the MOLP and OA isomers were calculated by DFT methods, and the possibility of solvent-mediated isomerization is discussed.}, doi = {10.1021/jacs.6b10609}, author = {Bertermann, Ruediger and Boehnke, Julian and Braunschweig, Holger and Dewhurst, Rian D. and Kupfer, Thomas and Muessig, Jonas H. and Pentecost, Leanne and Radacki, Krzysztof and Sen, Sakya S. and Vargas, Alfredo} } @inbook {43390, title = {Efficient methods for preparing silicon compounds}, booktitle = {Academic Press}, year = {2016}, chapter = {Efficient methods for preparing silicon compounds}, abstract = {

Efficient Methods for Preparing Silicon Compounds is a unique and valuable handbook for chemists and students involved in advanced studies of preparative chemistry in academia and industry. Organized by the various coordination numbers (from two to six) of the central silicon atom of the reported compounds, this book provides researchers with a handy and immediate reference for any compound or properties needed in the area. Edited by a renowned expert in the field, each chapter explores a different type of compound, thoroughly illustrated with useful schemes and supplemented by additional references. Knowledgeable contributors report on a broad range of compounds on which they have published and which are already used on a broad scale or have the potential to be used in the very near future to develop a new field of research or application in silicon chemistry. Includes contributions and edits from leading experts in the field Includes detailed chemical schemes and useful references for each preparative method Organized by the coordination numbers of the central silicon atom for each compound for easy navigation Serves as a go-to primer for researchers in novel compositions of silicon matter.

}, author = {Sen, Sakya S. and Roesky, H. W.} } @article { ISI:000378295200030, title = {Facile access to a Ge(II) dication stabilized by isocyanides}, journal = {Chemical Communications}, volume = {52}, number = {50}, year = {2016}, month = {MAY}, pages = {7890-7892}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Herein, we introduce isocyanide as a ligand in main group chemistry and describe the facile isolation of a Ge(II) dication. The reaction of 2,6-dimethylphenylisocyanide with GeCl2 leads to the formation of a Ge(II) dication with two [GeCl3](-) molecules as counter anions. The dicationic Ge(II) center is bound to four isocyanide ligands and also holds a lone pair of electrons. DFT calculations reveal that the dication is stabilized only by sigma-donation from the four isocyanide ligands. Natural population analysis gives a charge of +0.74 on the Ge(II) center, indicating that the positive charge is shared by the isocyanide substituents.

}, issn = {1359-7345}, doi = {10.1039/c6cc03789e}, author = {Swamy, V. S. V. S. N. and Yadav, Sandeep and Pal, Shiv and Das, Tamal and Vanka, Kumar and Sen, Sakya S.} } @inbook {43049, title = {Silanetriols and aluminosilicates}, booktitle = {Efficient methods for preparing silicon compounds}, year = {2016}, pages = {221-231}, publisher = {Academic Press, Elsevier}, organization = {Academic Press, Elsevier}, chapter = {17}, address = {Netherland}, author = {Sen, Sakya S. and Roesky, Herbert W.} } @inbook {43050, title = {Synthesis of silicon(II) compounds and their reactions}, booktitle = {Efficient methods for preparing silicon compounds}, year = {2016}, pages = {233-242}, publisher = {Academic Press, Elsevier}, organization = {Academic Press, Elsevier}, chapter = {18}, address = {Netherland}, author = {Sen, Sakya S. and Roesky, Herbert W.} } @article {43862, title = {C(sp(3))-F, C(sp(2))-F and C(sp(3))-H bond activation at silicon(II) centers}, journal = {Chemical Communication}, volume = {53}, year = {2017}, month = {SEP}, chapter = {9850-9853}, abstract = {

Silylene [PhC(NtBu)(2)SiN(SiMe3)(2)] (1) cleaves the C(sp(3))-H and C-F bonds of acetophenone and 1,1,1-trifluoroacetophenone, respectively, under mild conditions. The reaction is initiated via a nucleophilic attack from the oxygen to the silicon atom followed by C-F/H bond cleavage. The scope of C-F bond activation has further been extended with C6F6 and C6F5CF3.

}, keywords = {Boron triple bond, C-F Bond, Fluorinated Building-Block, H Activation, Ketones, N-heterocyclic carbenes, Oxodative Addition, Perfluorinated Arenes, Selective Activation, Transition-Metal Centers}, issn = {1359-7345}, doi = {10.1039/c7cc05145j}, author = {Swamy, V. S. V. S. N. and Parvin, Nasrina and Raj, K. Vipin and Sen, Sakya S.} } @article {43868, title = {Metal free mild and selective aldehyde cyanosilylation by a neutral penta-coordinate silicon compound}, journal = {Chemical Communications}, volume = {53}, year = {2017}, month = {JUN}, abstract = {This study demonstrates the preparation and structural characterization of a Si(IV) hydride (PhC(NtBu)(2)SiH(CH3)Cl) (1) and its use as a catalyst for the cyanosilylation of a variety of aldehydes. Compound 1 represents the first neutral penta-coordinate silicon(IV) species that catalyzes cyanosilylation of aldehydes under mild conditions.}, doi = {10.1039/c7cc03948d}, author = {Swamy, V. S. V. S. N. and Bisai, Milan Kumar and Das, Tamal and Sen, Sakya S.} } @article {43664, title = {Strikingly diverse reactivity of structurally identical silylene and stannylene}, journal = {Dalton Transactions}, volume = {46}, year = {2017}, month = {MAY}, pages = {6528-6532}, abstract = {The reactivity of structurally identical silylene and stannylene [PhC(NtBu)(2)EN(SiMe3)(2)] (E = Si (1) and Sn (2)) towards coinage metals has been explored. While 1 has the propensity to form an adduct with coinage metals (4 and 5), 2 undergoes a ligand exchange reaction with copper halides and silver triflate leading to PhC(NtBu) 2SnX (X = Br (6), Cl (7), and OSO2CF3 (8)) with concomitant formation of [M{N(SiMe3) (2)}] (M = Cu, Ag). However, with AgSbF6 both 1 and 2 led to ion pairs, 9(+) .SbF(6)(-)and 10(+) . SbF(6)(-)displaying weaker Ag center dot center dot center dot center dot F interactions in the latter.}, doi = {10.1039/c7dt01055a}, author = {Parvin, Nasrina and Dasgupta, Rajarshi and Pal, Shiv and Sen, Sakya S. and Khan, Shabana} } @article {43388, title = {Transition metal free catalytic hydroboration of aldehydes and aldimines by amidinato silane}, journal = {Dalton Transactions}, volume = {46}, year = {2017}, month = {FEB}, pages = {2420 - 2424}, abstract = {The transition metal free catalytic hydroboration of aldehydes and ketones is very limited and has not been reported with a well-defined silicon(iv) compound. Therefore, we chose to evaluate the previously reported silicon(iv) hydride [PhC(NtBu)2SiHCl2], (1) as a single component catalyst and found that it catalyzes the reductive hydroboration of a range of aldehydes with pinacolborane (HBpin) under ambient conditions. In addition, compound 1 can catalyze imine hydroboration. DFT calculation was carried out to understand the mechanism.}, doi = {10.1039/C6DT04893E}, author = {Bisai, Milan and Pahar, Sanjukta and Das, Tamal and Sen, Sakya S.} } @article {43866, title = {Unprecedented solvent induced inter-conversion between monomeric and dimeric silylene-zinc iodide adducts}, journal = {Dalton Transaction }, volume = {46}, year = {2017}, month = {SEP}, chapter = {11418-11424}, abstract = {

Usually, when a silylene reacts with a transition metal Lewis acid, it forms an adduct which could be either monomeric or dimeric. However, we present here that a silylene, [PhC(NtBu)(2)SiN(SiMe3)(2)] can form both monomeric [PhC(NtBu)(2)Si{N(SiMe3)(2)} -\> ZnI2]center dot THF (1) and dimeric [{PhC(NtBu)(2)}(N(SiMe3)(2))SiZnI,(mu-I)](2) (2) adducts upon reaction with ZnI2. The formation of 1 and 2 relies upon the solvent used for the reaction or crystallization. When the crystallization is carried out in THF complex 1 is formed, however, when the reaction and crystallization are performed in acetonitrile complex 2 is obtained. Both 1 and 2 were structurally authenticated and the nature of the Si-Zn bond in these complexes was determined by quantum chemical calculations. In addition, a spontaneous inter-conversion between 1 and 2 just by changing the solvents has been also observed; a feature presently not known for silylene-transition metal Lewis adducts.

}, keywords = {Bis(Silylene ), Carbene Complexes, Crystal -structure Determination, Dative bond, Lewis acid base reaction, Ligands, Main- group compounds, Reactivity, Silicon(II) Bis(Trimethylsilyl)Amide; Carbonyl-Complexes}, issn = {1477-9226}, doi = {10.1039/c7dt01823a}, author = {Yadav, Sandeep and Sangtani, Ekta and Dhawan, Diksha and Gonnade, Rajesh G. and Ghosh, Debashree and Sen, Sakya S.} } @article {44417, title = {Access to silicon(II)- and germanium(II)-indium compounds}, journal = {Organometallics}, volume = {37}, year = {2018}, month = {APR}, pages = {1206-1213}, abstract = {Despite the remarkable ability of N-heterocyclic silylene to act as a Lewis base and form stable Lewis adducts with group 13 elements such as boron, aluminum, and gallium, there has been no such comparable investigation with indium and the realization of a stable silylene-indium complex has still remained elusive. Similarly, a germylene-indium complex is also presently unknown. We describe herein the reactions of [PhC(NtBu)(2)SiN-(SiMe3)(2)] (1) and [PhC(NtBu)(2)GeN(SiMe3)(2)] (4) with InCl3 and InBr3 that have resulted in the first silylene-indium complexes, [PhC(NtBu)(2)Si{N(SiMe3)(2)}-> InCl3] (2) and [PhC(NtBu)(2)Si{N(SiMe3)(2)}-> InBr3] (3), as well as the first germylene-indium complexes, [PhC(NtBu)(2)Ge{N(SiMe3)(2)}-> InCl3] (5) and [PhC(NtBu)(2)Ge{N(SiMe3)(2)}-> InBr3] (6). The solid-state structures of all species have been validated by single-crystal X-ray diffraction studies. Note that 5 and 6 are the first structurally characterized organometallic compounds that feature a Ge-In single bond (apart from the compounds in Zintl phases). Theoretical calculations reveal that the Si(II)-> In bonds in 2 and 3 and the Ge(II)-> In bonds in 5 and 6 are dative bonds.}, doi = {10.1021/acs.organomet.8b00093}, author = {Pahar, Sanjukta and Karak, Suvendu and Pait, Moumita and Raj, K. Vipin and Vanka, Kumar and Sen, Sakya S.} } @article {44204, title = {Beyond hydrofunctionalisation: a well-defined calcium compound catalysed mild and efficient carbonyl cyanosilylation}, journal = {Chemistry-A European Journal}, volume = {24}, year = {2018}, month = {JAN}, pages = {1269-1273}, type = {Article}, abstract = {

Organocalcium compounds have been reported as efficient catalysts for various transformations, for cases in which one of the substrates contained an E-H (E=B, N, Si, P) bond. Here, we look at the possibility of employing an organocalcium compound for a transformation in which none of the precursors has a polar E-H bond. This study demonstrates the utilization of a well-defined amidinatocalcium iodide, [PhC(NiPr)(2)CaI] (1) for cyanosilylation of a variety of aldehydes and ketones with Me3SiCN under ambient conditions without the need of any co-catalyst. The reaction mechanism involves a weak adduct formation between 1 and Me3SiCN leading to the activation of the Si-C bond, which subsequently undergoes sigma-bond metathesis with a C=O moiety. Such a mechanistic pathway is unprecedented in alkaline earth metal chemistry. Experimental and computational studies support the mechanism.

}, keywords = {Ca catalysis, carbonyls, cyanosilylation, Density functional calculations, transition-metal free}, issn = {0947-6539}, doi = {10.1002/chem.201705795}, author = {Yadav, Sandeep and Dixit, Ruchi and Vanka, Kumar and Sen, Sakya S.} } @article {45465, title = { Cyclometallation of a germylene ligand by concerted metalation-deprotonation of a methyl group }, journal = {Dalton Transactions }, volume = {47}, year = {2018}, month = { NOV}, pages = { 15835-15844}, type = {Article }, abstract = {The reaction of [CH{(CMe)(2,6-iPr(2)C(6)H(3)N)}(2)]GeCl with LiN(SiMe3)(2) was previously reported, which led to the formation of a hetero-fulvene type germylene, [CH{(CMe)(C?CH2)(2,6-iPr(2)C(6)H(3)N)}(2)]Ge through the deprotonation of the C-H bond from the methyl substituents. In this paper, we attempted the analogous reaction with (Dipp)NCMeCHCOMeGeCl using LiN(SiMe3)(2) which gave rise to a metathesis product, (Dipp)NCMeCHCOMeGeN(SiMe3)(2) (2). However, the reactions of 2 with [M2Cl2(-Cl)(2)((5)-Cp*)(2)] (M = Rh and Ir) resulted in cyclometallated Rh and Ir complexes through the activation of the C-H bond from the germylene ligand. The complexes were characterized by single crystal X-ray analysis, which authenticated the presence of Ge-Rh and Ge-Ir bonds. DFT studies have been performed to understand the mechanism.}, issn = {1477-9226}, doi = { 10.1039/c8dt03166e}, author = {Bakthavachalam, K. and Dutta, Sayan and Arivazhagan, C. and Raghavendra, Beesam and Haridas, Anagha and Sen, Sakya S. and Koley, Debasis and Ghosh, Sundargopal} } @article {44458, title = {Easily accessible lithium compound catalyzed mild and facile hydroboration and cyanosilylation of aldehydes and ketones}, journal = {Chemical Communications}, volume = {54}, year = {2018}, month = {APR}, abstract = {Simple and readily accessible lithium compounds such as 2,6-ditertbutyl phenolate lithium (1a), 1,1{\textquoteright} dilithioferrocene (1b) and nacnac lithium (1c) are found to be efficient single site catalysts for hydroboration of...}, doi = {10.1039/C8CC02314J}, author = {Bisai, Milan and Das, Tamal and Vanka, Kumar and Sen, Sakya S.} } @article {45469, title = {Facile activation of Si-H bond by an electrophilic carbene}, journal = {Indian Chemical Society}, volume = {95}, year = {2018}, month = {JUL}, pages = {789-793}, type = {Article}, abstract = {Herein, we have explored the chemistry of 1,3-bis(2,6-di-isopropylphenyl)-5,5-dimethy1-4,6-diketopyrimidinyl-2-ylidene (1) with various silanes under mild conditions. The oxidative addition of Si-H bond of phenylsilane with DAC 1 affords the compound 2, which is unambiguously characterized by muitinuclear NMR spectroscopy, elemental analysis, and X-ray single crystal diffraction studies. Interestingly, DAC 1 activates silicon hydride bond of chlorosilanes at room temperature and results in the corresponding silylation products.}, issn = { 0019-4522}, author = {Swamy, V. S. V. S. N. and Kundu, Gargi and Sen, Sakya S.} } @article {44367, title = {Silicon-fluorine chemistry: from the preparation of SiF2 to C-F bond activation using silylenes and its heavier congeners}, journal = {Chemical Communications}, volume = {54}, year = {2018}, month = {MAY}, pages = {5046-5057}, type = {Article}, abstract = {This feature article is intended to provide a background to the history of the isolation of silicon(II) fluorides and the different synthetic methodologies used to generate them. Although first detected in the 1970s, the chemistry of silicon(II) fluorides has not encountered serious research efforts for a rather long period of time. This is somewhat surprising given the fact that the chemistry of compounds with divalent silicon has undergone a renaissance during last three decades. Recently, the interest in silicon(II) fluorides have been resparked with tremendous progress being achieved in this area, in particular, with respect to their synthesis and structural characterisation. The successful isolation of cyclic alkyl amino carbene (cAAC) stabilized silicon difluoride has completed the classic progression of SiF2, from a transient intermediate to spectroscopically detected molecule to a stable compound. The related germanium(II), tin(II), and lead(II) fluoride chemistry will also be discussed. Apart from the isolation of tetrel(II) fluorides, the use of compounds with low valent group 14 elements for the selective activation and functionalisation of C-F bonds has witnessed some remarkable advances, which will also be summarized in this feature article.}, doi = {10.1039/c8cc01816b}, author = {Sen, Sakya S. and Roesky, Herbert W.} } @article {46289, title = {Lithium compounds as single site catalysts for hydroboration of alkenes and alkynes}, journal = {Chemical Communications}, volume = {55}, year = {2019}, month = {OCT }, pages = {11711-11714}, type = {Article}, abstract = {

The hydroboration of alkenes and alkynes using easily accessible lithium compounds [2,6-di-tert-butyl phenolatelithium (1a) and 1,1 {\textquoteleft} dilithioferrocene (1b)] has been achieved with good yields, high functional group tolerance and excellent chemoselectivity. Deuterium-labeling experiments confirm the cis-addition of pinacolborane. The methodology has been further extended to myrcene, which undergoes selective 4,3-hydroboration. DFT calculations provide insights into the mechanism.

}, issn = {1359-7345}, doi = {10.1039/c9cc05783h}, author = {Bisai, Milan Kumar and Yadav, Sandeep and Das, Tamal and Vanka, Kumar and Sen, Sakya S.} } @article {46425, title = {Saturated N-heterocyclic carbene based thiele{\textquoteright}s hydrocarbon with a tetrafluorophenylene linker}, journal = {Chemistry-A European Journal}, year = {2019}, month = {NOV}, type = {Article; Early Access}, abstract = {

The synthesis of a SIPr [1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene] derived Kekule diradicaloid with a tetrafluorophenylene spacer (3) has been described. Two synthetic routes have been reported to access 3. The cleavage of C-F bond of C6F6 by SIPr in the presence of BF3 led to double C-F activated compound with two tetrafluoro borate counter anions (2), which upon reduction by lithium metal afforded 3. Alternatively, 3 can be directly accessed in one step by reacting SIPr with C6F6 in presence of Mg metal. Compounds 2 and 3 were well characterized spectroscopically and by single-crystal X-ray diffraction studies. Experimental and computational studies support the cumulenic closed-shell singlet state of 3 with a singlet-triplet energy gap (Delta ES-T) of 23.7 kcal mol(-1).

}, keywords = {C-F activation, Density functional calculations, fluorine, Kekule diradicaloids, saturated NHC}, issn = {0947-6539}, doi = {10.1002/chem.201904421}, author = {Kundu, Gargi and De, Sriman and Tothadi, Srinu and Das, Abhishek and Koley, Debasis and Sen, Sakya S.} } @article {46159, title = {Silylene induced cooperative B-H bond activation and unprecedented aldehyde C-H bond splitting with amidinate ring expansion}, journal = {Chemical Communications}, volume = {55}, year = {2019}, month = {MAR }, pages = {3536-3539}, type = {Article}, abstract = {

The addition of HBpin to PhC(NtBu)(2)SiN(SiMe3)(2) (1) results in the cleavage of the B-H bond in a cooperative fashion across the Si and amidinate-C sites. The reaction of 1 with benzaldehyde led to C-H bond activation with amidinate ring expansion leading to a five-membered heterocycle. In case of 4-fluorobenzaldehyde, a C-C bond coupling takes place leading to a dioxasilolane derivative as the major product.

}, issn = {1359-7345}, doi = {10.1039/c9cc00296k}, author = {Swamy, V. S. V. S. N. and Raj, K. Vipin and Vanka, Kumar and Sen, Sakya S. and Roesky, Herbert W.} } @article {46248, title = { Synthesis and reactivity of a hypersilylsilylene }, journal = {Inorganic chemistry}, volume = {58}, year = {2019}, month = {AUG}, pages = {10536-10542}, type = {Article}, abstract = {

Stabilization of an amidinatosilylene with a bulky tris(trimethylsilyl)silyl substituent was realized with the preparation of PhC(NtBu)(2)Si{Si(SiMe3)(3)} (1) from PhC(NtBu)(2)SiHCl2 with K{Si(SiMe3)(3)} in more than 90\% yield. The highly deshielded Si-29 NMR resonance (delta = 76.91 ppm) can be attributed to the absence of a pi-donating substituent. The molecular structure of 1 shows a trigonal-planar geometry around the Si-II center with a Si-II-Si-IV bond length of 2.4339(13) angstrom. A series of reactions of 1 with Me3NO, S, Se, and Te were performed. While siloxane derivatives (2 and 3) are obtained from reactions with Me3NO, silachalcogenones (4-6) are formed with other chalcogens. The presence of Si=E (E = S, Se, and Te) bonds in 4-6 have been confirmed by single crystal X-ray studies. Silaoxirane (7) formation was observed when 1 was treated with acetone, demonstrating the importance of the tris(trimethylsilyl)silyl group to kinetically and thermodynamically protect the silaoxirane derivative with less bulky substituents on the C atom.

}, doi = {10.1021/acs.inorgchem.9b00418}, author = {Bisai, Milan Kumar and Swamy, V. S. V. S. N. and Das, Tamal and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {46680, title = {Access to diverse germylenes and a six-membered dialane with a flexible beta-diketiminate}, journal = {Chemical Communications}, volume = {56}, year = {2020}, month = {OCT}, pages = {11871-11874}, type = {Article}, abstract = {

A nacnac-based tridentate ligand containing a picolyl group (L) was employed to isolate chlorogermylene (1). The reaction of1with another equivalent of GeCl2 center dot dioxane surprisingly gave pyridylpyrrolide-based chlorogermylene (2)viaC-N bond cleavage and C-C coupling, while with AlCl3, it afforded a transmetalated product,4. The reaction of L with AlH3 center dot NMe2Et led to an unusual cyclohexane type six-membered dialane heterocycle (5).

}, issn = {1359-7345}, doi = {10.1039/d0cc05202g}, author = {Pahar, Sanjukta and Swamy, V. S. V. S. N. and Das, Tamal and Gonnade, Rajesh G. and Vanka, Kumar and Sen, Sakya S.} } @article {46716, title = {Amidinato germylene-zinc complexes: synthesis, bonding, and reactivity}, journal = {Chemistry-An Asian Journal}, volume = {15}, year = {2020}, month = {OCT }, pages = {3116-3121}, type = {Article}, abstract = {

Despite the explosive growth of germylene compounds as ligands in transition metal complexes, there is a modicum of precedence for the germylene zinc complexes. In this work, the synthesis and characterization of new germylene zinc complexes [PhC(NtBu)(2)Ge{N(SiMe3)(2)}-\> ZnX2](2)(X= Br (2) and I (3)) supported by (benz)-amidinato germylene ligands are reported. The solid-state structures of2and3have been validated by single-crystal X-ray diffraction studies, which revealed the dimeric nature of the complexes, with distorted tetrahedral geometries around the Ge and Zn center. DFT calculations reveal that the Ge-Zn bonds in2and3are dative in nature. The reaction of2with elemental sulfur resulted in the first structurally characterized germathione stabilized ZnBr(2)complexes PhC(NtBu)(2)Ge(=S){N(SiMe3)(2)}-\> ZnBr2(5). Therefore, the Ge=S in5is in-between Ge-S single and Ge=S double bond length, owing to the coordination of a sulfur lone pair of electrons to ZnBr2.

}, keywords = {DFT, Germathione, Germylene, X-ray Structure, zinc}, issn = {1861-4728}, doi = {10.1002/asia.202000807, Early Access Date = SEP 2020}, author = {Yadav, Sandeep and Kumar, Rohit and Raj, K. Vipin and Yadav, Prashant and Vanka, Kumar and Sen, Sakya S.} } @article {46679, title = {Cyanosilylation by compounds with main-group elements: an odyssey}, journal = {ACS Omega}, volume = {5}, year = {2020}, month = {OCT}, pages = {25477-25484}, type = {Review}, abstract = {

The past few decades have seen remarkable headways in the structural and reaction chemistry of compounds with heavier main-group elements. In recent years, there is an ongoing effort to derive catalytic chemistry involving main-group compounds, driven by their lower costs and higher terrestrial abundances. Here, a survey on the state-of-the-art in the development of cyanosilylation methodology by compounds with heavier main-group elements has been given. Once dominated by transition metals, the field has matured to embrace the majority of the main-group elements including aluminum, silicon, and calcium. Of particular focus will be how the mechanism of cyanosilylation involving compounds with main-group elements differs from those of transition metals.

}, issn = {2470-1343}, doi = {10.1021/acsomega.0c03293}, author = {Pahar, Sanjukta and Kundu, Gargi and Sen, Sakya S.} } @article {46599, title = {Stepwise nucleophilic substitution to access saturated N-heterocyclic carbene haloboranes with boron-methyl bonds}, journal = {Organometallics}, volume = {39}, year = {2020}, month = {DEC}, pages = {4696-4703}, type = {Article}, abstract = {

Compounds of boranes with N-heterocyclic carbenes are known, yet little attention has been paid to NHC compounds of boron bearing methyl and halogen moieties together. The reason can be attributed to the hazardous methyldichloroborane (MeBCl2), which ignites in air. We describe here convenient solution-phase access to SIDipp.MeBCl2 (SIDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) (3) by a salt metathesis reaction of SIDipp.BCl3 (2) with MeLi. Replacement of the chlorine atoms of 3 with stepwise addition of AgOTf led to the formation of SIDipp.MeBCl(OTf) (4) and SIDipp.MeB(OTf)2 (5). In the case of 4, all of the substituents on the boron atom are different. Subsequently, we extended our synthetic approach to the amidinate system and prepared PhC(NtBu)2B(Me)Cl (7) from the reaction of PhC(NtBu)2BCl2 (6) with MeLi.

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.0c00691}, author = {Kundu, Gargi and Pahar, Sanjukta and Tothadi, Srinu and Sen, Sakya S.} } @article {46956, title = {Tale of biphenyl and terphenyl substituents for structurally diverse ketiminato magnesium, calcium and germanium complexes}, journal = {Chemistry-An Asian Journal}, volume = {15}, year = {2020}, month = {MAR}, pages = {820-827}, type = {Article}, abstract = {

In this paper, we have used two N,O-ketiminato ligands (L1 and L2) with biphenyl and terphenyl substituent on the nitrogen atom. Deprotonation of L1 with KN(SiMe3)(2) and subsequent reaction with MgI2 led to a homoleptic dinuclear magnesium complex (1) with a Mg2O2 four-membered ring. Deprotonation with nBuLi and subsequent reaction with MgI2 afforded a unusual dinuclear magnesium complex (2) with a Mg2O2 ring. Extension of the ligand for calcium resulted in a trinuclear calcium complex (3) with six four-membered Ca2O2 rings. We could not isolate any chelating complex when L2 was used as a ligand, and only oxygen bound magnesium (4) and calcium (5) adducts were isolated. DFT studies were performed to understand this dissimilar behavior. More diverse results were obtained when lithiated L1 and L2 were treated with germanium dichloride. We were able to stabilize a monomeric germylene monochloride (7) with L1. However, with L2, an unusual ligand scrambling, and a C-C coupling take place, leading to the formation of a secondary carbocation with GeCl3- as a counter-anion (8). Besides, a germanium dichloride adduct (9) bound to the oxygen center of the ligand was obtained as the minor product.

}, keywords = {calcium, Germylene, ligand, Magnesium, X-ray Structure}, issn = {1861-4728}, doi = {10.1002/asia.201901801, Early Access Date = FEB 2020}, author = {Kumar, Rohit and Yadav, Sandeep and Gour, Kritika and Sangtani, Ekta and Ranjan Dash, Soumya and Raja, Abhishekram and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {46910, title = {Transmetallation vs adduct: diverse reactivity of N,O-ketiminato germylene with [Cp*MCl2](2) (M = Rh or Ir; Cp* = eta(5)-C5Me5) and MCl5 (M = Nb and Ta)}, journal = {Journal of Organometallic Chemistry}, volume = {911}, year = {2020}, month = {APR }, pages = {121142}, type = {Article}, abstract = {

The reactions of the germylenes, [(Dipp)NCMeCHCORGeCl] (1a: R = Me, 1b: R = Ph) with [Ir2Cl2(mu-Cl)(2)(eta(5)-Cp*)(2)] led to the formation of the adducts [(Dipp)NCMeCHCORGeClIrCl2Cp*] (3a: R = Me and 3b: R = Ph). On the other hand, [Rh2Cl2(mu-Cl)(2)(eta(5)-Cp*)(2)] does not react with the germylenes (1a and 1b). When the reactions of 1a and 1b are carried out with [Cp*TaCl4], the reaction led to decomposition. The reaction of 1a or 1b with TaCl5 yielded the transmetallated products [(Dipp)NCMeCHCORTaCl4] (4a: R = Me, 4b: R = Ph) with the extrusion of GeCl2. Our theoretical studies show that for, the insertion of TaCl5 to 1a and the formation of 4a with concomitant elimination of GeCl2 is energetically favourable. Extrusion of SnCl2 is also observed when the corresponding stannylene, [(Dipp)NCMeCHCOMeSnCl] was reacted with TaCl5. All these compounds have been characterized by H-1 and C-13 NMR spectroscopy, elemental analysis and the constitution of compounds 1b, 3b, and 4a were confirmed by single-crystal X-ray crystallography. (C) 2020 Elsevier B.V. All rights reserved.

}, keywords = {Adduct formation, Germylenes, Iridium, Ketoiminate, Tantalum, Transmetallation}, issn = {0022-328X}, doi = {10.1016/j.jorganchem.2020.121142}, author = {Raghavendra, Beesam and Bakthavachalam, K. and Das, Tamal and Roisnel, Thierry and Sen, Sakya S. and Vanka, Kumar and Ghosh, Sundargopal} } @article {47595, title = {Access to a variety of Ge(II) and Sn(II) compounds through substitution of hypersilyl moiety}, journal = {Organometallics}, volume = {40}, year = {2021}, month = {AUG }, pages = {2651-2657}, type = {Article}, abstract = {We have prepared amidinato-germylene (3) and -stannylene (4) with a tris(trimethylsilyl)silyl substituent and subsequently substituted the hypersilyl moiety by reacting 3 with chlorophosphines, which led to phosphino germylenes (5 and 6) with concomitant liberation of (Me3Si)(3)SiCl. Exploiting the fluoride affinity of the silicon atom, we have prepared pentafluoropyridyl germylene (7) and -stannylene (8) by reacting 3 and 4 with C5F5N with simultaneous elimination of (Me3Si)(3)SiF. These are the first examples of aryl germylenes or stannylenes prepared via C-F bond activation of a perfluoroarene. The reaction of 4 with Me3NO resulted in a novel Sn2O2 ring (9). All compounds were characterized by single-crystal X-ray structure determination studies.}, issn = {0276-7333}, doi = {10.1021/acs.organomet.1c00306}, author = {Bisai, Milan Kumar and Ajithkumar, V. S. and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {47644, title = {Deoxygenative hydroboration of primary and secondary amides: a catalyst-free and solvent-free approach}, journal = {Chemical Communications}, volume = {57}, year = {2021}, month = {OCT }, pages = {10596-10599}, type = {Article}, abstract = {In contrast to the recent reports on catalytic hydroboration of amides to amines with pinacolborane (HBpin), a simple catalyst-free and solvent-free method for the hydroboration of a variety of amides has been realized. To get the mechanistic insights, DFT calculations have been performed.}, issn = {1359-7345}, doi = {10.1039/d1cc04148g}, author = {Kumar, Rohit and Bisai, Milan Kumar and Jain, Shailja and Vanka, Kumar and Sen, Sakya S.} } @article {47422, title = {Diverse reactivity of carbenes and silylenes towards fluoropyridines}, journal = {Chemical Communications}, volume = {57}, year = {2021}, month = {MAY }, pages = {4428-4431}, type = {Article}, abstract = {

The reaction of IDipp with C5F5N led to functionalization of all three carbon atoms of the imidazole ring with HF2- as the counter-anion (1). Reactivity with 2,3,5,6-tetrafluoropyridine gives only C-F bond activation leaving C-H bonds intact (5b). The reaction of SIDipp with C5F5N in the presence of BF3 afforded the ring cleavage product (3). Analogous reactions with silylene led to oxidative addition at the Si(II) center.

}, issn = {1359-7345}, doi = {10.1039/d1cc01401c, Early Access Date = MAR 2021}, author = {Kundu, Gargi and Ajithkumar, V. S. and Bisai, Milan Kumar and Tothadi, Srinu and Das, Tamal and Vanka, Kumar and Sen, Sakya S.} } @article {47086, title = {Diverse reactivity of hypersilylsilylene with boranes and threecomponent reactions with aldehyde and HBpin}, journal = {Inorganic Chemistry}, volume = {60}, year = {2021}, month = {FEB }, pages = {1654-1663}, type = {Article}, abstract = {

The recently reported hypersilylsilylene PhC-(NtBu)(2)SiSi(SiMe3)(3) (1) reacts with BH3, 9-BBN, and PhBCl2 to yield the respective Lewis acid base adducts 2-4, respectively. Compound 4 undergoes isomerization to form a ring expansion product 5. The same silylene was found to initially form an adduct with HBpin (6) and subsequently isomerized to 7 via the rupture of the B-H bond of HBpin (7), where the hydride was bound to the carbon atom of the amidinate ligand and the Bpin unit was attached to the silicon center. Surprisingly, the reaction of 1 with HBcat results in PhC(NtBu)(2)Bcat (8). Subsequently, we have shown that HBcat forms the same product when it reacts with related silylene PhC(NtBu)(2)SiN(SiMe3)(3) (1{\textquoteright}). With all of these reactions in hand, we ponder if silylene can activate two small molecules at one time. In this work, we delineate the three-component reactions of silylenes 1 and 1{\textquoteright} with 4-fluorobenzaldehyde and HBpin, which afforded unusual coupling products, 9 and 10, respectively. Note that 9 and 10 were prepared from the cleavage of the B-H and C=O bonds by silylene in a single reaction and are the first structurally attested Si-C-O-B coupled products.

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.0c03137}, author = {Bisai, Milan Kumar and Swamy, V. S. V. S. N. and Raj, K. Vipin and Vanka, Kumar and Sen, Sakya S.} } @article {47058, title = {Lithium compound catalyzed deoxygenative hydroboration of primary, secondary and tertiary amides}, journal = {Dalton Transactions}, volume = {50}, year = {2021}, month = {FEB}, pages = {2354-2358}, type = {Article}, abstract = {

A selective and efficient route for the deoxygenative reduction of primary to tertiary amides to corresponding amines has been achieved with pinacolborane (HBpin) using simple and readily accessible 2,6-di-tert-butyl phenolate lithium center dot THF (1a) as a catalyst. Both experimental and DFT studies provide mechanistic insight.

}, issn = {1477-9226}, doi = {10.1039/d1dt00364j}, author = {Bisai, Milan Kumar and Gour, Kritika and Das, Tamal and Vanka, Kumar and Sen, Sakya S.} } @article {47655, title = {Pyridylpyrrolido ligand in Ge(II) and Sn(II) chemistry: synthesis, reactivity and catalytic application}, journal = {Dalton Transactions}, volume = {50}, year = {2021}, month = {NOV}, pages = {16678-16684}, type = {Article}, abstract = {In our previous communication, we have reported the synthesis of a new chlorogermylene (B) featuring a pyridylpyrrolido ligand. This study details the preparation of a series of new germylenes and stannylenes starting from B. A transmetallation reaction between B and SnCl2 led to the analogous chlorostannylene (1) with the simultaneous elimination of GeCl2. This is a very unusual example of transmetallation between two elements of the same group. The preparation of 1via lithiation led to the formation of 2 as a side product, where the ortho C-H bond of the pyridine ring was activated and functionalized with a Bu-n moiety. Subsequently, B and 1 were used as precursors to generate germylene (4) and stannylene (5) featuring tris(trimethylsilyl)silyl (hypersilyl) moieties. We also prepared tetrafluoropyridyl germylene (6) by reacting 4 with C5F5N with the simultaneous elimination of (Me3Si)(3)SiF by utilizing the fluoride affinity of the silicon atom. As there is scarcity of Sn(II) compounds as single-site catalysts, we investigated 5 as a catalyst towards the hydroboration of aldehydes, ketones, alkenes and alkynes. All the compounds have been characterized by single-crystal X-ray diffraction and by state of the art spectroscopic studies.}, issn = {1477-9226}, doi = {10.1039/d1dt03136h}, author = {Pahar, Sanjukta and Sharma, Vishal and Tothadi, Srinu and Sen, Sakya S.} } @article {47647, title = {Reactivities of silaimines with boranes: from cooperative B-H bond activation to donor stabilized silyl cation}, journal = {Organometallics}, volume = {40}, year = {2021}, month = {JUL}, pages = {2133-2138}, type = {Article}, abstract = {The recently published silylene with a tris(trimethylsilyl) group, PhC(NtBu)(2)SiSi(SiMe3)(3) (1), was reacted with the organic azides such as SiMe3N3 and AdN(3) to form the respective hypersilylsilaimines, PhC(NtBu)(2)Si(=NR)Si(SiMe3)(3) 2 (R = SiMe3) and 3 (R = Ad). The B-H bond of HBpin or HBcat was split across the Si=N bond upon reaction with 2, which generated 4 and 5, respectively. However, we could not obtain the crystals of 4 and 5 appropriate for X-ray diffraction. Subsequently, we performed the analogous reactions with a related silaimine PhC(NtBu)(2)Si(=NSiMe3)N(SiMe3) 2 (2{\textquoteright}) and isolated similar B-H bond activated products 6 and 7. The reaction of 2{\textquoteright} with HBCl2 resulted in donor stabilized silyl cations (8 and 9) supported by an amidinate ligand.}, issn = {0276-7333}, doi = {10.1021/acs.organomet.1c00273}, author = {Bisai, Milan Kumar and Sharma, Vishal and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {47621, title = {Readily available lithium compounds as catalysts for the hydroboration of carbodiimides and esters}, journal = {Journal of Organometallic Chemistry}, volume = {949}, year = {2021}, month = {SEP 15}, pages = {121924}, type = {Article}, abstract = {Selective and efficient hydroboration of esters and carbodiimides to alcohols and amines by two welldefined and readily accessible lithium complexes, 2,6-di-tert-butyl phenolate lithium (1a ) and 1,1{\textquoteright}-dilithioferrocene (1b ) are described. A range of aliphatic, aromatic, and cyclic esters with various functional groups were selectively converted into the corresponding boronate esters. Similarly, the single hydroboration of carbodiimides with aliphatic and aromatic substituents on the nitrogen atoms was studied. A possible mechanistic pathway of the hydroboration of carbodiimides with HBpin has been proposed using NMR studies and DFT calculations. These reactions are convenient alternatives to stoichiometric hydride reduction or hydrogenation. The employing of lithium complexes is also significant, because of the need to find cheap and green alternatives to noble metal complexes. (C) 2021 Elsevier B.V. All rights reserved.}, issn = {0022-328X}, doi = {10.1016/j.jorganchem.2021.121924}, author = {Bisai, Milan Kumar and Gour, Kritika and Das, Tamal and Vanka, Kumar and Sen, Sakya S.} } @article {47382, title = {Substrate, catalyst, and solvent: the triune nature of multitasking reagents in hydroboration and cyanosilylation}, journal = {Organometallics}, volume = {40}, year = {2021}, month = {APR}, pages = {1104-1112}, type = {Article}, abstract = {

A truly green chemical process would avoid the use of an external catalyst, while still achieving high efficiency. This has been realized in the very recent past for hydroboration, cyanosilylation, acetalization, and the aza-Michael addition, among other reactions. The current combined computational and experimental study unlocks the secret to how this highly desirable outcome is accomplished: one of the reactants in the process also acts as the catalyst. Specifically, this is shown (i) for the important hydroboration reaction, with pinacolborane (HBpin) as the hydroborating reagent and benzaldehyde, acetophenone, benzoic acid and p-methoxyphenylacetylene as the hydroborated substrates, and (ii) for cyanosilylation, with trimethylcyanosilane (TMSCN) as the cyanosilylating agent and benzaldehyde as the substrate. The mechanistic understanding thus gained has then been further exploited experimentally to bring hydroboration and cyanosilylation closer to experimental conditions in catalysis. These insights can potentially be expanded to the rapidly growing area of solvent-free and internal catalyst chemistry.

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.1c00070}, author = {Dixit, Ruchi and Bisai, Milan Kumar and Yadav, Sandeep and Yadav, Vinita and Sen, Sakya S. and Vanka, Kumar} } @article {47654, title = {Unsymmetrical sp(2)-sp(3) disilenes}, journal = {Angewandte Chemie-International Edition}, volume = {60}, year = {2021}, month = {SEP }, pages = {20706-20710}, type = {Article}, abstract = {Disilenes with differently coordinated silicon atoms are not known. Here, we have shown the high yield synthesis of a range of disilenes (2-4 and 6) upon reaction of a hypersilyl silylene PhC(NtBu)(2)SiSi(SiMe3)(3) (1) with aliphatic chlorophosphines. The most striking characteristic of these disilenes is the presence of two differently coordinated Si atoms (one is three-coordinated, the other four-coordinated). The analogous reaction with Ph2PCl did not afford the desired disilene, but, surprisingly, led to the first tetraphosphinosilane (8). DFT calculations were performed to understand the bonding in disilenes and differences in reactivity of the complexes.}, keywords = {chlorophosphine, DFT, disilene, hypersilylsilylene}, issn = {1433-7851}, doi = {10.1002/anie.202107847}, author = {Bisai, Milan Kumar and Das, Tamal and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {47901, title = {Hypersilyl substituent in heavier low-valent group 14 chemistry}, journal = {European Journal of Inorganic Chemistry}, volume = {2022}, year = {2022}, month = {APR }, pages = {e202200071}, type = {Review}, abstract = {

The isolation of unusual compounds with low-valent main-group elements would not have been possible without the development of a series of sterically demanding ligands with bulky substituents. While early literature recognizes the advent of the sterically demanding tris(trimethylsilyl)silyl (SiMe3)(3)Si- group, also known as hypersilyl group, to stabilize species with new coordination modes for the main group elements, it has largely been more recent studies that have utilized this group for isolating stable compounds with low-valent main-group elements. Such compounds are not only interesting from the structure-bonding point of view but showcase potential for small molecule activation under ambient conditions. This review will cover the recent developments in stabilizing unusual compounds with group 14 elements using the exceptionally strong sigma-donor properties and pronounced steric effects of the hypersilyl moiety, emphasizing their synthesis, structure, and reactivity.

}, keywords = {Germylenes, Hydroboration, Hypersilyl, silylenes, Stannylenes}, issn = {1434-1948}, doi = {10.1002/ejic.202200071}, author = {Gour, Kritika and Bisai, Milan Kumar and Sen, Sakya S.} } @article {48154, title = {Luminescent magnesium complexes with intra- and inter-ligand charge transfer}, journal = {Chemical Communications}, volume = {58}, year = {2022}, month = {OCT}, pages = {11843-11846}, type = {Article}, abstract = {

Herein, we report two 2,2{\textquoteright}-pyridylpyrrolide (PyPyrH) ligand supported magnesium complexes (1 and 2), which demonstrate bright luminescence with a quantum yield of 22\% and 14\% in the solid state, respectively. Theoretical calculations reveal that their emissive properties originate from the intra- and inter-ligand charge transfer.

}, issn = {1359-7345}, doi = {10.1039/d2cc04142a}, author = {Kumar, Rohit and Pahar, Sanjukta and Chatterjee, Joy and Dash, Soumya Ranjan and Gonnade, Rajesh G. and Vanka, Kumar and Sen, Sakya S.} } @article {48141, title = {Monomeric magnesium catalyzed alkene and alkyne hydroboration}, journal = {Chemistry-A European Journal}, volume = {28}, year = {2022}, month = {OCT }, type = {Article}, abstract = {

In this work, two monomeric magnesium alkyl complexes (1 and 2) were prepared using bis(phosphino)carbazole framework and among them 1 has been used as a catalyst for hydroboration of alkenes and alkynes with pinacolborane (HBpin). A broad variety of aromatic and aliphatic alkenes and alkynes were efficiently reduced. Anti-Markovnikov regioselective hydroboration of alkenes and alkynes was achieved, which was confirmed by deuterium-labelling experiments. The work represents the first example of the use of magnesium in homogeneous catalytic hydroboration of alkene with broad substrate scope. Experimental mechanistic investigations and DFT calculations provided insights into the reaction mechanism. Finally, the hydroboration protocol was extended to terpenes.

}, keywords = {carbazole, Magnesium, monomeric complexes, phosphorous, X-ray Structure}, issn = {0947-6539}, doi = {10.1002/chem.202201896}, author = {Kumar, Rohit and Dutta, Sayan and Sharma, Vishal and Singh, Praval P. and Gonnade, Rajesh G. and Koley, Debasis and Sen, Sakya S.} } @article {48142, title = {Nucleophilic substitution at a coordinatively saturated five-membered NHC center dot haloborane centre}, journal = {Inorganics}, volume = {10}, year = {2022}, month = {JUL}, pages = {97}, type = {Article}, abstract = {

In this paper, we have used a saturated five-membered N-Heterocyclic carbene (5SIDipp = 1,3-bis-(2,6-diisopropylphenyl)imidazolin-2-ylidine) for the synthesis of SNHC-haloboranes adducts and their further nucleophilic substitutions to put unusual functional groups at the central boron atom. The reaction of 5-SIDipp with RBCl2 yields Lewis-base adducts, 5-SIDipp center dot RBCl2 [R = H (1), Ph (2)]. The hydrolysis of 1 gives the NHC stabilized boric acid, 5-SIDipp center dot B(OH)(3) (3), selectively. Replacement of chlorine atoms from 1 and 2 with one equivalent of AgOTf led to the formation of 5-SIDipp center dot HBCl(OTf) (4) and 5-SIDipp center dot PhBCl(OTf) (5a), where all the substituents on the boron atoms are different. The addition of two equivalents of AgNO3 to 2 leads to the formation of rare di-nitro substituted 5-SIDipp center dot BPh(NO3)(2) (6). Further, the reaction of 5-SIDipp with B(C6F5)(3) in tetrahydrofuran and diethyl ether shows a frustrated Lewis pair type small molecule activated products, 7 and 8.

}, keywords = {NHC-haloboranes, nucleophilic substitution, saturated NHC, tetra-coordinate boron}, doi = {10.3390/inorganics10070097}, author = {Kundu, Gargi and Tothadi, Srinu and Sen, Sakya S.} } @article {48126, title = {Six-membered saturated NHC-stabilized borenium cations: isolation of a cationic analogue of borinic acid}, journal = {Inorganic Chemistry}, volume = {61}, year = {2022}, month = {AUG}, pages = {12991-12997}, type = {Article}, abstract = {

The reaction of six-membered saturated NHC [1,3-di(2,6-diisopropylphenyl) tetrahydropyrimidine-2-ylidene; henceforth abbreviated as 6-SIDipp] with PhBCl2 yields a Lewis base adduct, 6-SIDipp.PhBCl2 (1), which readily undergoes nucleophilic substitution reaction with AgNO3, leading to the single (2) and double (3) substitution of both chlorides with ONO2 moieties at the boron atom. The reaction of 1 with 1 equiv of AlCl3 resulted in a borenium cation of composition [6-SIDipp.B(Ph)Cl]+ (4) with AlCl4- as the counteranion. Although borenium cations with different substituents on boron have been reported, a structurally characterized phenylchloroborenium cation remains unknown. Similarly, the reaction of 1 with triflic acid provides the first representative of a new class of borenium cations bearing one hydroxyl and one phenyl group on boron (5), a cationic analogue of borinic acid. Ph-BN H Diphenylborinic acid

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.2c00611}, author = {Kundu, Gargi and Balayan, Kajal and Tothadi, Srinu and Sen, Sakya S.} } @article {48149, title = {Substitution at sp(3) boron of a six-membered NHC center dot BH3: convenient access to a dihydroxyborenium cation}, journal = {Chemical Communications}, volume = {58}, year = {2022}, month = {MAR }, pages = {3783-3786}, type = {Article}, abstract = {

Herein, we have undertaken the synthesis and investigated the reactivity of a 6-membered saturated NHC borane adduct (1). Direct electrophilic halogenation of 1 with a stoichiometric amount of I-2 led to NHC boryl iodides, 6-SIDipp center dot BH2I (2) and 6-SIDipp center dot BHI2 (3), which were further reacted with various nucleophiles to give novel 6-SIDipp based mono and disubstituted boranes with OTf (4 and 6) or ONO2 (5 and 7) functional groups. The addition of Br-2/H2O to 1 smoothly results in a dihydroxyborenium cation (8).

}, issn = {1359-7345}, doi = {10.1039/d1cc06816d}, author = {Kundu, Gargi and Ajithkumar, V. S. and Raj, K. Vipin and Vanka, Kumar and Tothadi, Srinu and Sen, Sakya S.} } @article {48051, title = {Tridentate NacNac stabilized tin and nickel complexes: access to a monomeric nickel hydride and its catalytic application}, journal = {Inorganic Chemistry}, volume = {61}, year = {2022}, month = {OCT}, pages = {17370-17377}, type = {Article}, abstract = {

The transmetalation reaction of picolyl-supported tridentate nacnac germylene monochloride [2,6-iPr2-C6H3NC-(Me)CHC(Me)NH(CH2py)]GeCl (1) (py = pyridine) with SnCl2 results in an analogous stannylene chloride (2). The three -coordinated stannylenium cation [{2,6-iPr2-C6H3NC(Me)CHC-(Me)NH(CH2py)}Sn]+ with SnCl3- as a counteranion (3) has been generated through the abstraction of chloride ligand from 2 using an additional equivalent of SnCl2. Instead of forming a donor-acceptor complex, 2 undergoes a facile redox trans-metalation reaction with Ni(COD)2 (COD = cyclooctadiene) and CuCl to afford analogous nickel and copper complexes [2,6-iPr2-C6H3NC(Me)CHC(Me)NH(CH2py)]MCl [M = Ni (4) and Cu (5)]. The reactions of 4 with potassium tri-sec-butylborohydride (commonly known as K-selectride) and AgSbF6 provide access to monomeric Ni(II) hydride, [2,6-iPr2-C6H3NC(Me)CHC(Me)NH(CH2py)]NiH (6) and a Ni(II) cation, [{2,6-iPr2- C6H3NC(Me)CHC(Me)NH(CH2py)}Ni][SbF6] (7), respectively. 6 was found to be an effective catalyst for the hydroboration of amides.

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.2c03227}, author = {Pahar, Sanjukta and Sharma, Vishal and Mahata, Biplab and George, Christy P. and Sharma, Himanshu and Vanka, Kumar and Sen, Sakya S.} } @article {48162, title = {Versatile chemistry of six-membered NHC with boranes: bromination at sp(3) borane, activation of the B-H bond of HBpin, and ring expansion of NHC}, journal = {Dalton Transactions}, volume = {51}, year = {2022}, month = {OCT}, pages = {14452-14457}, type = {Article}, abstract = {

The NHC.borane chemistry has been majorly restricted to imidazol-2-ylidene classes of carbenes. In our previous communication, we reported the synthesis of 6-SIDipp center dot BH3 [6-SIDipp = 1,3-di(2,6-diisopropylphenyl) tetrahydropyrimidine-2-ylidene] and its electrophilic substitution reaction with iodine. Here, we have shown selective bromination of a 6-SIDipp stabilized sp(3) B-H bond. Treatment of 1.2 equivalents of N-bromosuccinamide with 6-SIDipp center dot BH3 gives a mixture of mono- and disubstituted products 6-SIDipp center dot BH2Br (1) and 6-SIDipp center dot BHBr2 (2). However, the reactions with alkyl bromides or carbon tetrabromide resulted in 6-SIDipp center dot BH2Br (1) selectively. Exploration of the chemistry of 6-SIDipp with BHCl2 and 9-BBN (9-borabicyclo[3.3.1]nonane) led to mono-6-SIDipp adducts 3 and 6a. Furthermore, 6a undergoes ring expansion to afford a seven-membered product, 6b, under mild conditions. Unlike BHCl2 or 9-BBN, the B-H bond of HBpin undergoes oxidative addition upon reaction with 6-SIDipp, epitomizing the first example (7) of a B-H bond insertion at NHCs. The analogous reactivity with HBcat led to a tetra-hydropyrimidinium salt with B(cat)(2) as a counteranion (8).

}, issn = {1477-9226}, doi = {10.1039/d2dt01707e}, author = {Kundu, Gargi and Dixit, Ruchi and Tothadi, Srinu and Vanka, Kumar and Sen, Sakya S.} } @article {48032, title = {Well-defined calcium compound catalyzes trimerization of arylisocyanates into 1,3,5-triarylisocyanurates}, journal = {ChemCatChem}, volume = {14}, year = {2022}, month = {JUN }, pages = {e202101788}, type = {Article}, abstract = {

We report the synthesis of a calcium complex (2) bearing a tetradentate monoanionic ligand with a diaminoethane core and phenolate and pyridine peripheral donors. Single crystal X-ray studies on 2 revealed that LiI was also co-crystallized, leading to a four-membered ring with four different elements. 2 was found to be an efficient catalyst for the cyclotrimerization of a variety of aromatic isocyanates under mild conditions.

}, keywords = {calcium, Cyclotrimerization, Isocyanurates, Tetradentate ligand}, issn = {1867-3880}, doi = {10.1002/cctc.202101788}, author = {Kumar, Rohit and Sharma, Vishal and Jain, Shailja and Sharma, Himanshu and Vanka, Kumar and Sen, Sakya S.} } @article {48753, title = {Activation of the olefinic C-H bond of NHC and NHO by perimidine-based silicon and germanium compounds}, journal = {Organometallics}, volume = {42}, year = {2023}, month = {JUL}, pages = {1909-1917}, type = {Article}, abstract = {

In this manuscript, several backbonegermylene-functionalized zwitterioniccompounds were prepared conveniently from the corresponding N-heterocycliccarbenes or N-heterocyclic olefins in a single step through backboneC-H activation. Our initial motivation was to generate a silylenefrom C10H6(Me3SiN)(2)SiHCl(2) using ItBu [ItBu= (1,3-ditert-butyl)imidazol-2-ylidene], but instead, the reactionled to deprotonation from the imidazolium backbone of ItBu, forming the imidazolium salt with a silyl backbone at the C4position (3). We presumed that the reaction proceededthrough the generation of an ephemeral silylene. We subsequently preparedthe analogous germylene (4) and reacted it with IDipp[IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene], ItBu, and IDipp=CH2. Spectroscopic and crystallographicanalysis of these complexes revealed that, in all cases, there wasdeprotonation from the backbone and formation of zwitterionic products(5-7). When the hydrogen in the NHCbackbone was replaced with methyl groups such as IDipp(Me) (1,3-bis(2,6-diisopropylphenyl)-4,5-dimethylimidazol-2-ylidene),simple adduct formation occurred, exemplified by the isolation ofIDipp(Me)\& BULL;Ge(NSiMe3)(2)C10H6 (8).

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.3c00167}, author = {Gour, Kritika and Pramanik, Debjit and Dash, Soumya Ranjan and Tothadi, Srinu and Vanka, Kumar and Sen, Sakya S.} } @article {48687, title = {On the competition between six-membered and five-membered NHC towards alane centered ring expansion}, journal = {Chemical Communications}, volume = {59}, year = {2023}, month = {JUL}, pages = {8540-8543}, type = {Article}, abstract = {

The combination of 6-SIDipp center dot AlH3 (1) and 5-IDipp resulted in the ring expansion of 6-NHC, while the five-membered NHC remained unchanged, which was subsequently explained by DFT studies. Besides, the substitution chemistry of 1 was also studied with TMSOTf and I-2, which gave rise to the substitution of a hydride by triflate or iodide ligands.

}, issn = {1359-7345}, doi = {10.1039/d3cc02063k}, author = {Balayan, Kajal and Sharma, Himanshu and Vanka, Kumar and Ravindranathan, Sapna and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {48263, title = {Controlled reduction of isocyanates to formamides using monomeric magnesium}, journal = {Chemical Communications}, volume = {59}, year = {2023}, month = {FEB}, pages = {2255-2258}, type = {Article}, abstract = {

This work describes a transition metal-free methodology involving an efficient and controlled reduction of isocyanates to only formamide derivatives using pinacolborane (HBpin) as the hydrogenating agent and a bis(phosphino)carbazole ligand stabilized magnesium methyl complex (1) as the catalyst. A large number of substrates undergo selective hydroboration and give exclusively N-boryl formamides.

}, issn = {1359-7345}, doi = {10.1039/d3cc00036b}, author = {Kumar, Rohit and Sharma, Vishal and Banerjee, Subhrashis and Vanka, Kumar and Sen, Sakya S.} } @article {48755, title = {Enhancing diradical character of chichibabin{\textquoteright}s hydrocarbon through fluoride substitution}, journal = {ChemPlusChem}, volume = {88}, year = {2023}, month = {AUG}, pages = {e202300273}, type = {Article}, abstract = {

In this work, 5-SIDipp [SIDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene] (1) derived Chichibabin{\textquoteright}s hydrocarbon with an octafluorobiphenylene spacer (3) has been reported. The addition of two equivalents of 5-SIDipp with decafluorobiphenyl in presence of BF3 gives the double C-F bond activated imidazolium salt with two tetrafluoroborate anions, 2. Further reduction of 2 gives the fluorine substituted 5-SIDipp based Chichibabin{\textquoteright}s hydrocarbon, 3. Quantum chemical calculations suggested a singlet state of 3 with a singlet-triplet energy gap (?ES-T) of 3.7 kcal mol(-1), which is substantially lower with respect to the hydrogen substituted NHC-based Chichibabin{\textquoteright}s hydrocarbons (10.7 kcal mol(-1), B3LYP). As a result, the diradical character (y) of 3 (y=0.62) is also noticeably higher than the hydrogen substituted CHs (y=0.41-0.43). The ?ES-T was found to be higher in CASSCF (22.24 kcal mol(-1)) and CASPT2 (11.17 kcal mol(-1)) for 3 and the diradical character (d) is 44.6 \%.

}, keywords = {C-F Bond Activation, Chichibabin \& PRIME, DFT, N-Heterocyclic carbene, s Hydrocarbon}, issn = {2192-6506}, doi = {10.1002/cplu.202300273}, author = {Kundu, Gargi and Dash, Soumya Ranjan and Kumar, Ravi and Vanka, Kumar and Ghosh, Aryya and Sen, Sakya S.} } @article {48738, title = {Six-membered NHC stabilized monomeric zinc complexes}, journal = {European Journal of Inorganic Chemistry}, volume = {26}, year = {2023}, month = {JUL}, pages = {e202300167}, type = {Article}, abstract = {

This paper describes the rare use of a 6-membered saturated N-heterocyclic carbene (NHC) known as 1,3-di(2,6-diisopropylphenyl) tetrahydropyrimidine-2-ylidene (abbreviated as 6-SI-Dipp) as a ligand in zinc chemistry. We report on the investigation of the reactions between 6-SI-Dipp and ZnX2, which resulted in a range of new monomeric 6-SIDipp center dot ZnX2 complexes (X=Et (1), Cl (2), Br (3), and I (4)). We also prepared a new NHC zinc complex where the two substituents of the zinc atom are different, 6-SIDipp center dot Zn(Et)Br (7) through the reaction of the proligand [6-SIDippH]Br with ZnEt2. We have observed that the reactions of complex 1 with sulfur and HBpin led to the removal of the ZnEt2 moiety, resulting in the formation of a C=S double bond and a B H activation product, respectively. Lastly, the reaction of 1 with five-membered NHCs led to the exchange of carbene and the formation of either 5-IDipp center dot ZnEt2 (8) or 5-SIDipp center dot ZnEt2 (9).

}, keywords = {Lewis adduct, NHC, X-ray diffraction, zinc}, issn = {1434-1948}, doi = {10.1002/ejic.202300167}, author = {Gour, Kritika and Kundu, Gargi and Dash, Soumya Ranjan and Vanka, Kumar and Tothadi, Srinu and Sen, Sakya S.} } @article {48720, title = {Synthesis of Si(IV)- and Ge(II)-substituted amines, hydrazone, and hydrazine from hypersilyl germylene}, journal = {Organometallics}, volume = {42}, year = {2023}, month = {OCT}, pages = {2983-2990}, type = {Article}, abstract = {

This study investigates the reactivity of a hypersilyl germylene [PhC-(NtBu)(2)GeSi-(SiMe3)(3)] (1) with various organic compounds including azides, diazoalkanes, 1,2-diphenylhydrazine, and trifluoroacetophenone. The reactivity observed in these reactions is driven by the insertion of the organic fragment between a silicon and germanium bond. This leads to the formation of novel compounds, including an amine featuring three different substituents from three different elements of group 14. When reacting with Me3SiCHN2, we observed the insertion of the diazoalkane fragment in an end-on fashion into the Ge-Si bond. An analogous trend was observed in reactions with 1,2-diphenylhydrazine and trifluoroacetophenone, where the N-N and C-O fragments were inserted into the Ge-Si bond. Multinuclear NMR and single-crystal X-ray diffraction analyses were conducted to characterize the newly synthesized compounds.

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.3c00318}, author = {Ajithkumar, V. S. and Ghanwat, Pratiksha B. and Raj, K. Vipin and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {48769, title = {Taming the parent oxoborane}, journal = {Chemical Science}, volume = {14}, year = {2023}, month = {JUN}, pages = {5894-5898}, type = {Article}, abstract = {

Despite recent advancements in the chemistry of multiply bound boron compounds, the laboratory isolation of the parent oxoborane moiety, HBO has long remained an unsolved and well-recognized challenge. The reaction of 6-SIDipp(.)BH3 [6-SIDipp = 1,3-di(2,6-diisopropylphenyl)tetrahydropyrimidine2-ylidene] with GaCl3 afforded an unusual boron-gallium 3c-2e compound (1). The addition of water to 1 resulted in the release of H-2 and the formation of a rare acid stabilized neutral parent oxoborane, LB(H)]O (2). Crystallographic and density functional theory (DFT) analyses support the presence of a terminal B=O double bond. Subsequent addition of another equivalent of water molecule led to hydrolysis of the B-H bond to the B-OH bond, but the {\textquoteleft}B=O{\textquoteright} moiety remained intact, resulting in the formation of the hydroxy oxoborane compound (3), which can be classified as a monomeric form of metaboric acid.

}, issn = {2041-6520}, doi = {10.1039/d3sc01544k}, author = {Kundu, Gargi and Amrutha, P. R. and Raj, K. Vipin and Tothadi, Srinu and Vanka, Kumar and Sen, Sakya S.} } @article {48690, title = {Zwitterionic disilanylium from an unsymmetrical disilene}, journal = {Chemical Communications}, volume = {59}, year = {2023}, month = {FEB }, pages = {1669-1672}, type = {Article}, abstract = {

The reaction of PhC(NtBu)2SiSi(SiMe3)(3) (1) with Me3SiCH(2)Cl afforded an unsymmetrical sp(2)-sp(3) disilene, 2, with concomitant elimination of Me3SiCl. The analogous reaction with PhC(NtBu)2SiCl resulted in the oxidative addition of the C-Cl bond at the Si(II) atom (3). The reactions of 2 with sulfur and selenium led to compounds with Si=E (E=S (4) and Se (5)) double bonds. Tellurium reacted differently with 2 and furnished a zwitterionic compound, 6.

}, issn = {1359-7345}, doi = {10.1039/d2cc06954g}, author = {Bisai, Milan Kumar and Ajithkumar, V. S. and Raj, K. Vipin and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {48971, title = {Access to NHC-Boryl mono- and bis-selenide and utility as mild selenium transfer reagent including to the C-F bond}, journal = {Chemistry- a european journal}, volume = {30}, year = {2024}, month = {JAN }, type = {Article}, abstract = {

Reactions of 5-SIDipp \& sdot; BH3 (5-SIDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene) (1) with diphenyldiselenide provide access to 5-SIDipp-boryl mono- (5-SIDipp \& sdot; BH2SePh) (2) and bis-selenide (5-SIDipp \& sdot; BH(SePh)2) (3). The facile cleavage of the B-Se bond makes 2 a neutral source of selenium nucleophiles in substitutions reactions with benzyl bromides, and provide access to the corresponding selenoethers. The direct transformations of one of the C(sp2)-F bonds of C5F5N and C6F5CF3 to C-Se bonds have also been achieved by the use of 2 without employing transition-metal catalysts. While it was previously established that C6F6 could undergo complete defluoroselenation under harsh conditions, we successfully achieved partial defluorination of C6F6 by employing 2 as a mild selenide transfer reagent. During the formation of C-Se bonds through the cleavage of C-F bonds, the potential by-product NHC \& sdot; BH2F undergoes ring expansion of the NHC, leading to the formation of the six-membered diaazafluoroborinane (7). Access to NHC \& sdot; boryl mono- and bis-selenides from NHC \& sdot; BH3 has been achieved. The boryl mono selenide has been demonstrated to function as a selenium transfer reagent, enabling the synthesis of selenoethers from benzyl bromide. Additionally, it can also facilitate the conversion of the challenging aromatic C-F bond to a C-Se bond, resulting in concomitant ring expansion of NHC \& sdot; haloborane.image

}, keywords = {boron, C-F Bond Activation, N-Heterocyclic carbene, Ring expansion, Selenium}, issn = {0947-6539}, doi = {10.1002/chem.202302984}, author = {Kundu, Gargi and Amrutha, P. R. and Tothadi, Srinu and Sen, Sakya S.} } @article {49393, title = {Activation of carbon disulfide by a hypersilyl germylene}, journal = {Dalton Transactions}, volume = {53}, year = {2024}, month = {JUL}, type = {Article}, abstract = {

In this work, the insertion of CS2 into the Ge-Si bond of PhC(NtBu)2Ge-Si(SiMe3)3 (1) has been investigated, resulting in the formation of PhC(NtBu)2Ge-C( 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 S)-S-Si(SiMe3)3 (2). Interestingly, the addition of NHC to 2 allows the release of NHCCS2 with concomitant regeneration of 1. Addition of another equivalent of 1 or an analogous hypersilyl silylene, [PhC(NtBu)2Si-Si(SiMe3)3], to 2 led to the formation of compounds with a GeS (3) or a SiS (4) bond. In this work, the insertion of CS2 into the Ge-Si bond of PhC(NtBu)2Ge-Si(SiMe3)3 (1) has been investigated, resulting in the formation of PhC(NtBu)2Ge-C(S)-S-Si(SiMe3)3 (2).

}, issn = {1477-9226}, doi = {10.1039/d4dt01573h}, author = {Ajithkumar, V. S. and Khilari, Nripen and Ghanwat, Pratiksha B. and Venugopal, Geethu and Koley, Debasis and Sen, Sakya S.} } @article {48938, title = {Lanthanide mimicking by magnesium for oxazolidinone synthesis}, journal = {Chemistry- a european journal}, volume = {30}, year = {2024}, month = {JAN }, type = {Article}, abstract = {

In the last decade, magnesium complexes have emerged as a viable alternative to transition-metal catalysts for the hydrofunctionalization of unsaturated bonds. However, their potential for advanced catalytic reactions has not been thoroughly investigated. To address this gap, we have developed a novel magnesium amide compound (3) using a PNP framework that is both bulky and flexible. Our research demonstrates that compound 3 can effectively catalyze the synthesis of biologically significant oxazolidinone derivatives. This synthesis involves a tandem reaction of hydroalkoxylation and cyclohydroamination of isocyanate using propargyl alcohol. Furthermore, we conducted comprehensive theoretical calculations to gain insights into the reaction mechanism. It is important to note that these types of transformations have not been reported for magnesium and would significantly enhance the catalytic portfolio of the 7th most abundant element. A monomeric magnesium compound was employed as a catalyst for the cascade cyclization of propargylic alcohol and isocyanate, resulting in the formation of pharmaceutically significant oxazolidinone derivatives. This transformation, previously attributed solely to transition metals or lanthanides, signifies a noteworthy advancement.image

}, keywords = {catalysis, Magnesium, oxazolidinone, pincer ligand, Sustainability}, issn = {0947-6539}, doi = {10.1002/chem.202303478}, author = {Kumar, Rohit and Mahata, Biplab and Gayathridevi, S. and Raj, K. Vipin and Vanka, Kumar and Sen, Sakya S.} } @article {49374, title = {Saturated NHC-stabilized borenium, boronium, hydride-bridged boron cations, and a bora-acyl chloride}, journal = {ORGANOMETALLICS}, volume = {43}, year = {2024}, month = {JUN }, pages = {1355-1361}, keywords = {activation, BORINIUM, Chemistry}, issn = {0276-7333}, doi = {10.1021/acs.organomet.4c00139}, author = {Kundu, Gargi and Amrutha, P. R. and Tothadi, Srinu and Sen, Sakya S.} } @article {49271, title = {Stereodivergent sila-germylenation vs. sila-stannylenation of an internal alkyne}, journal = {CHEMICAL COMMUNICATIONS}, volume = {60}, year = {2024}, month = {SEP }, pages = {9837-9840}, type = {Journal Article}, keywords = {DIVERSE REACTIVITY, H BOND ACTIVATION, hydrides}, issn = {1359-7345}, doi = {10.1039/d4cc02101k}, author = {Ajithkumar, V. S. and Ghanwat, Pratiksha B. and Saha, Sougata and Pati, Swapan K. and Sen, Sakya S.} } @article {49027, title = {Tridentate NacNac tames T-shaped nickel(I) radical}, journal = {Chemistry- a european journal}, volume = {30}, year = {2024}, month = {FEB}, type = {Article}, abstract = {

The reaction of a nickel(II) chloride complex containing a tridentate beta-diketiminato ligand with a picolyl group [2,6-iPr2-C6H3NC(Me)CHC(Me)NH(CH2py)]Ni(II)Cl (1)] with KSi(SiMe3)3 conveniently afforded a nickel(I) radical with a T-shaped geometry (2). The compound{\textquoteright}s metalloradical nature was confirmed through electron paramagnetic resonance (EPR) studies and its reaction with TEMPO, resulting in the formation of a highly unusual three-membered nickeloxaziridine complex (3). When reacted with disulfide and diselenide, the S-S and Se-Se bonds were cleaved, and a coupled product was formed through carbon atom of the pyridine-imine group. The nickel(I) radical activates dihydrogen at room temperature and atmospheric pressure to give the monomeric nickel hydride. A thermally stable, T-shaped, nickel(I) radical was straightforward obtained by reduction of a tridentate nacnac nickel(II) chloride with KSi(TMS)3. The metalloradical character of the compound was demonstrated by the formation of a highly unusual nickeloxaziridine complex upon addition of TEMPO. The Ni(I) species displays a rich chemistry towards activation S-S, and Se-Se bond leading to unusual C-C coupled product as well as dihydrogen activation at room temperature and atmospheric pressure to generate monomeric nickel hydride.+image

}, keywords = {C-C Bond formation, Hydrogen Activation, Metalloradical, Nickel, Tridentate nacnac}, issn = {0947-6539}, doi = {10.1002/chem.202303957}, author = {Pahar, Sanjukta and Sharma, Vishal and Raj, K. Vipin and Sangole, Mayur P. and George, Christy P. and Singh, Kirandeep and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {49279, title = {Uncovering diverse reactivity of NHCs withdiazoalkane: C-H activation, C=C bond formation,and access to N-heterocyclic methylenehydrazine}, journal = {Chemical Science}, volume = {15}, year = {2024}, month = {NOV}, pages = {18387-18394}, type = {Article}, abstract = {

N-heterocyclic carbenes (NHCs) have attracted significant attention due to their strong sigma-donating capabilities, as well as their transition-metal-like reactivity towards small molecules. However, their interaction with diazoalkanes remains understudied. In this manuscript, we explore the reactivity of a series of stable carbenes, encompassing a wide range of electronic properties, with Me3SiCHN2. 5-SIPr activates the C-H bond of Me3SiCHN2, resulting in the formation of a novel diazo derivative (1), while carbenes such as 5-IPr, 6-SIPr, and diamido carbene yield N-heterocyclic methylenehydrazine derivatives (3, 4, and 8). The reaction of Me3SiCHN2 with 5-ItBu unexpectedly leads to the formation of a triazole ring linked with the imidazole moiety via a CC double bond (6) alongside the azine product (7). Substituting the diazoalkane with diazoester consistently yields azine derivatives (9-12 and 14). Only in the case of 5-ItBu, an imidazolium salt with tetrazenide anion (13) was obtained as a side product. The reaction of 4 with HCl resulted in the desilylprotonation to form a salt, 5a, which undergoes deprotonation upon using bases such as Et3N and KHMDS to form N-heterocyclic methylene hydrazine, 5. Theoretical calculations have been conducted to elucidate the diverse mechanisms underlying product formation.

}, issn = {2041-6520}, doi = {10.1039/d4sc05740f}, author = {Balayan, Kajal and Sharma, Himanshu and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {49265, title = {Unprecedented C-F bond cleavage in perfluoronaphthalene during cobaltocene reduction}, journal = {DALTON TRANSACTIONS}, volume = {53}, year = {2024}, month = {NOV }, pages = {17789-17793}, type = {Journal Article}, issn = {1477-9226}, doi = {10.1039/d4dt02791d}, author = {Kundu, Gargi and Pramanik, Debjit and Dash, Soumya Ranjan and Kumar, Ravi and Sangole, Mayur and Tothadi, Srinu and Ghosh, Aryya and Vanka, Kumar and Singh, Kirandeep and Sen, Sakya S.} } @article {49897, title = {C=C insertion over N=C=O of allyl isocyanate into the Ge-Si bond of a germylene}, journal = {European Journal of Inorganic Chemistry}, volume = {28}, year = {2025}, month = {SEP}, type = {Article}, abstract = {

Two isocyanates are reacted with the germylene, PhC(NtBu)(2)Ge-Si(SiMe3)(3) (1). Phenyl isocyanate undergoes catalytic cyclotrimerization with 1 leading to 1,3,5-triphenyl isocyanurate (2), while allyl isocyanate undergoes both cyclotrimerization and the C=C bond insertion between the Ge-Si bond. The constitution of 3 is determined by single-crystal X-ray studies. The contrasting reactivity pattern is explained by comprehensive density functional theory studies.

}, keywords = {Cyclotrimerization, Density functional theory, Germylene, Insertion, isocyanates}, issn = {1434-1948}, doi = {10.1002/ejic.202500305}, author = {Ajithkumar, V. S. and Khilari, Nripen and Ghanwat, Pratiksha B. and Koley, Debasis and Sen, Sakya S.} } @article {49674, title = {Development of six-membered saturated cyclic diaminocarbenes in main-group chemistry}, journal = {Dalton Transactions}, volume = {54}, year = {2025}, month = {JUN}, pages = {9113-9124}, type = {Review}, abstract = {

In recent years, there has been a remarkable surge in the utilization of saturated N-heterocyclic carbenes (NHCs) as ligands in main group chemistry. While the field has predominantly focused on five-membered NHCs and cyclic alkyl(amino) carbene (CAAC) ligands, the investigation of six-membered NHCs (6-NHCs) has only just begun. Despite possessing higher nucleophilicity than their five-membered counterparts, 6-NHCs have been less explored due to their lack of structural rigidity. This feature article aims to highlight recent developments in 6-NHCs in only main group chemistry. Exciting new studies have demonstrated the activation of B-H bonds in HBpin, ring expansion from a six-membered to a seven-membered ring under ambient conditions, and the stabilization of transient units {\textquoteleft}{\textquoteleft}H-B 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 O{\textquoteright}{\textquoteright} and {\textquoteleft}{\textquoteleft}(OH)BO{\textquoteright}{\textquoteright}, among other intriguing phenomena. A major focus of this review is on synthetic approaches for 6-NHC-stabilized main-group compounds and their unusual properties, as revealed by spectroscopic and crystallographic data. While the chemistry of 6-NHCs is still in its nascent stage, the findings presented in this feature article underscore the need for its exploration and further investigation. Furthermore, this review provides valuable insights into effective synthetic methods for creating new 6-NHCmain group (B, Al, Si, P, Zn, etc.) complexes, along with mechanistic explanations for some of these reactions. These advances hold great promise for the future development of this exciting and rapidly evolving field of N-heterocyclic carbene chemistry.

}, issn = {1477-9226}, doi = {10.1039/d5dt00648a}, author = {Kundu, Gargi and Sen, Sakya S.} } @article {49616, title = {Germylene mediated reductive C-C and C-N coupling of an isocyanide and its device application}, journal = {Angewandte Chemie-International Edition}, volume = {64}, year = {2025}, month = {FEB }, type = {Article}, abstract = {

We have demonstrated a unique reductive coupling of 4-iodophenyl isocyanide, facilitated by a perimidine-based N-heterocyclic germylene (NHGe), which yields a bis-spirogerma compound featuring simultaneous C-C and C-N bond formation. This reaction, which leads to the oxidation of germanium from +2 to +4, represents a significant departure from previously documented isocyanide-germylene interactions. The product exhibits extensive conjugation across its bicyclic C4Ge2N2 framework, conferring distinct photophysical properties, including prominent orange luminescence in both solution and solid states. The photophysical properties are supported by the TD-DFT calculations confirming an n -\>pi* transition. The potential application of this compound in optoelectronic devices, particularly as a hole transport layer in PbS quantum dot solar cells, is also explored, with promising preliminary results.

}, keywords = {Germylene, hole transport layer, Isocyanide, reductive coupling}, doi = {10.1002/anie.202417052}, author = {Gour, Kritika and Pramanik, Debjit and Dash, Soumya Ranjan and Shinde, Dipak Dattatray and Venugopal, Geethu and Vanka, Kumar and Rath, Arup K. and Sen, Sakya S.} } @article {49807, title = {Hypersilylsilylene-supported Ni(0) toluene and Ni(II) complexes with catalytic application}, journal = {Organometallics}, volume = {44}, year = {2025}, month = {NOV}, pages = {2646-2653}, type = {Article}, abstract = {

The reaction of Ni(COD)2 with [PhC(NtBu)2SiSi(SiMe3)3] (1) in toluene results in the formation of an 18-electron silylene-Ni(0) toluene complex (2). The analogous reaction with 1,3-DFB instead of toluene affords the C-H activation followed by ring walking leading to the allylic cyclooctene adduct, the (eta 3-C8H13)Ni(II) complex (3). DFT calculations were carried out to elucidate the mechanism as well as to gain insight into why 1,3-DFB undergoes C-H bond activation instead of C-F bond activation. The use of NiCl2DME permits access to 16-electron (tetrylene)2NiCl2 (Si(4) and Ge(5)) species, and 4 was later used as a catalyst for the C-N coupling reaction.

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.5c00303}, author = {Ajithkumar, V. S. and Bisai, Milan Kumar and Ghanwat, Pratiksha B. and Raj, K. Vipin and Singh, Geetika and Vanka, Kumar and Sen, Sakya S.} } @article {49693, title = {Magnesium-catalyzed primary, secondary, and tertiary amide hydroboration}, journal = {Inorganic Chemistry}, volume = {64}, year = {2025}, month = {JUN}, pages = {13405-13414}, type = {Article}, abstract = {

Catalytic hydroboration of amides is highly important because the resultant amines are commonly found in natural products, pharmaceuticals, agrochemicals, dyes, and other applications. In comparison to the conventional reduction of amides using (over)stoichiometric reductants, hydroboration of amides using magnesium compounds represents a green and sustainable approach because magnesium is both Earth abundant and environmentally benign. However, there is only one report on magnesium-catalyzed deoxygenative hydroboration of secondary and tertiary amides. Here, we describe the synthesis and structural authentication of two new magnesium compounds (1 and 2) featuring a flexible PNP ligand and the utilization of 2 as a catalyst for the pinacolborane-mediated reduction of primary, secondary, and tertiary amides to amines. The reaction scope is explored, and a mechanism is proposed based on experimental and theoretical insights.

}, issn = {0020-1669}, doi = {10.1021/acs.inorgchem.5c01787}, author = {Mahata, Biplab and Devaraj, V. and Dash, Soumya Ranjan and Gonnade, Rajesh G. and Vanka, Kumar and Sen, Sakya S.} } @article {49518, title = {Magnesium-ligand cooperation in breaking the O-H and C-H bonds of water and diazoalkane}, journal = {Organometallics}, volume = {44}, year = {2025}, month = {MAR}, pages = {875-881}, type = {Article}, abstract = {

In our previous paper, we reported that the reaction of a tridentate nacnac ligand with a pendant picolyl group, with KHMDS and MgI2, resulted in the formation of a homoleptic hexacoordinate magnesium compound. Here, we show that the analogous reaction of the ligand with CH3MgBr led to a heteroleptic magnesium bromide species (1). Attempts to generate the magnesium hydride species from 1 led to the dearomatization of the pyridine ring, and the resulting product was a magnesium hydroxide (3) presumably generated due to an adventitious amount of water. The reaction of the ligand with nBu2Mg afforded a unique dearomatized magnesium species (2) in high yield. Theoretical calculations reveal the presence of a nonbonding orbital on the magnesium, susceptible to nucleophilic attack. Indeed, the reaction of 2 with H2O/D2O cleaves the O-H/D bond via magnesium-ligand cooperation and generates a magnesium hydroxide (4 and 5). In addition, 2 reacts with Me3SiCHN2 and cleaves the C-H bond to generate another unusual, well-defined magnesium compound with a bridging isocyanide moiety (6) via migration of the SiMe3 group from the carbon to the nitrogen atom. The latter can be described as a dimer of magnesium isocyanamide. DFT calculations were performed to understand the electronic structures of the synthesized molecules.

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.5c00031}, author = {Sharma, Vishal and Dash, Soumya Ranjan and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {49704, title = {Manganese(i)-catalyzed dehydrogenative borylation of terminal alkynes}, journal = {Dalton Transactions}, volume = {54}, year = {2025}, month = {JUL}, pages = {10426-10432}, type = {Article}, abstract = {

Compounds containing carbon-boron bonds serve as valuable intermediates for constructing more complex molecules by transforming these bonds into other carbon-element bonds. The catalytic dehydrogenative borylation of carbon-hydrogen bonds using HBpin presents an appealing method for synthesizing carbon-boron bonds. While this approach has been extensively explored with noble metals for various types of carbon-hydrogen bonds, its application with manganese-based catalysts remains rare. This study explores a dehydrogenative borylation process employing an Earth-abundant transition metal catalyst, FcbpyMn(CO)3Br (Mn(i)), in combination with HBpin under mild conditions. Arylalkynes featuring electron-withdrawing, electron-donating, and heteroaryl substituents yielded good to excellent results. Thorough DFT calculations were performed to understand the mechanism.

}, issn = {1477-9226}, doi = {10.1039/d5dt00577a}, author = {Ghanwat, Pratiksha B. and Bora, Debashree and Pandya, Rinu and Vanka, Kumar and Saha, Biswajit and Sen, Sakya S.} } @article {49715, title = {Sila[1]ferrocenophanes with Bulky Substituents}, journal = {European Journal of Inorganic Chemistry}, volume = {28}, year = {2025}, month = {MAY }, type = {Article}, abstract = {

In this study, sila[1]ferrocenophanes with sterically bulky groups such as tris(trimethylsilyl) or N-heterocyclic iminato located at the bridging silicon atom are synthesized. The reactions of silicon-bound chloride in Fe(eta 5-C5H4)2SiCl2 (1) with K[Si(SiMe3)3] and silylated N-heterocyclic imine result in sila[1]ferrocenophanes 2 and 3 with bulky silicon- and nitrogen-based substituents at the ansa-bridge via elimination of KCl and Me3SiCl. Subsequently, the reduction of 1 is attempted using 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (popularly known as Mashima reagent), which leads to the elimination of Me3SiCl and generation of 1,4-dihydropyrazine-spanned sila[1]ferrocenophanes (4). All the compounds are structurally characterized.

}, keywords = {ansa-bridges, ferrocenophanes, hypersilyls, Mashima reagents, N-heterocyclic imines}, issn = {1434-1948}, doi = {10.1002/ejic.202500120}, author = {Ajithkumar, V. S. and Bisai, Milan Kumar and Yuvaraj, K. and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {49683, title = {Synthesis of diamido N-heterocyclic imines (DAC = NH) via staudinger or reductive N-N bond cleavage approach}, journal = {Organometallics}, volume = {44}, year = {2025}, month = {MAY}, pages = {1129-1133}, type = {Article}, abstract = {

This report communicates the first examples of N-heterocyclic imines based on electrophilic diamido carbenes (DACs). While 2 is prepared by classical Staudinger synthesis, 4 is obtained via an unusual reductive N-N bond cleavage of an azine by HCl. The exocyclic C=N bond lengths in 2 and 4 are substantially shorter than those based on N-heterocyclic carbenes and cyclic (alkyl)(amino)carbene reflecting the electrophilic character of DACs.

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.5c00120}, author = {Balayan, Kajal and Sharma, Himanshu and Vanka, Kumar and Gonnade, Rajesh G. and Sen, Sakya S.} } @article {50078, title = {Kekule diradicaloid with a naphthalene spacer}, journal = {Organometallics}, volume = {45}, year = {2026}, month = {MAR }, pages = {624-627}, type = {Article}, abstract = {

The availability of a diverse array of carbenes led to the generation of a catalog of carbene based Kekule diradicaloids, but the linker in such molecules is mostly limited to phenylene or biphenylene. Here we have prepared a closed-shell Kekule diradicaloid (2) separated by a naphthalene moiety and stabilized by two capping 5-SIDipp [5-SIDipp = 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene] from the reduction of the corresponding dication (1). The combined experimental and computational studies confirm that 2 is in a closed-shell singlet state exhibiting a singlet-triplet energy difference (Delta ES-T) of 18.7 kcal/mol, which is considerably lower than Thiele{\textquoteright}s version (29.1 kcal/mol).

}, issn = {0276-7333}, doi = {10.1021/acs.organomet.5c00508}, author = {Kundu, Gargi and Pramanik, Debjit and Dash, Soumya Ranjan and Kumar, Ravi and Tothadi, Srinu and Ghosh, Aryya and Vanka, Kumar and Sen, Sakya S.} } @article {50091, title = {Unveiling the reactivity of N-heterocyclic methylene hydrazines}, journal = {Dalton Transactions}, volume = {55}, year = {2026}, month = {APR}, pages = {5432-5436}, type = {Article}, abstract = {

We present the first reactivity profile of N-heterocyclic methylene hydrazines, revealing distinct competition between steric and electronic control. Reactions with HCl are electronically driven, resulting in protonation at the proximal nitrogen, while the bulky Lewis acid B(C6F5)3 coordinates to the sterically accessible distal nitrogen. Additionally, we demonstrate that these scaffolds undergo spontaneous, base-free HCN elimination with tetracyanoethylene (TCNE) to form highly conjugated molecules with significantly reduced HOMO-LUMO gaps.

}, issn = {1477-9226}, doi = {10.1039/d6dt00611f}, author = {Balayan, Kajal and Biswas, Arindam and Sharma, Himanshu and Tiwari, Prabhakar and Vanka, Kumar and Gonnade, Rajesh G. and Rath, Arup K. and Sen, Sakya S.} }