@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 {44410, title = {Understanding Ziegler{\textendash}Natta catalysis through your laptop}, journal = {Resonance}, year = {2017}, month = {NOV}, abstract = {This article focuses on the different components that make up Ziegler{\textendash}Natta olefin polymerization systems and shows how investigating the interactions between these components through computational approaches provide crucial information about the chemistry of these systems. Hence, the necessity of theory acting as a counterpoint to experiment is revealed, underlining the importance of computational chemistry in attacking important problems of the day.}, author = {Raj, K. Vipin and Kumar, Vanka} } @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 {44511, title = {Iron Catalyzed Hydroformylation of Alkenes under Mild Conditions: Evidence of an Fe(II) Catalyzed Process}, journal = {Journal of the American Chemical Society}, volume = {140}, year = {2018}, month = {MAR }, pages = {4430-4439}, abstract = {

Earth abundant, first row transition metals offer a cheap and sustainable alternative to the rare and precious metals. However, utilization of first row metals in catalysis requires harsh reaction conditions, suffers from limited activity, and fails to tolerate functional groups. Reported here is a highly efficient iron catalyzed hydroformylation of alkenes under mild conditions. This protocol operates at 10-30 bar syngas pressure below 100 degrees C, utilizes readily available ligands, and applies to an array of olefins. Thus, the iron precursor [HFe(CO)(4)](-)[Ph3PNPPh3](+) (1) in the presence of triphenyl phosphine catalyzes the hydroformylation of 1-hexene (S2), 1-octene (S1), 1-decene (S3), 1-dodecene (S4), 1-octadecene (S5), trimethoxy(vinyl)silane (S6), trimethyl(vinyl)silane (S7), cardanol (S8), 2,3-dihydrofuran (S9), allyl malonic acid (S10), styrene (S11), 4-methylstyrene (S12), 4-iBu-styrene (S13), 4-tBu-styrene (S14), 4-methoxy styrene (S15), 4-acetoxy styrene (S16), 4-bromo styrene (S17), 4-chloro styrene (S18), 4-vinylbenzonitrile (S19), 4-vinylbenzoic acid (S20), and allyl benzene (S21) to corresponding aldehydes in good to excellent yields. Both electron donating and electron withdrawing substituents could be tolerated and excellent conversions were obtained for S11-S20. Remarkably, the addition of 1 mol \% acetic acid promotes the reaction to completion within 16-24 h. Detailed mechanistic investigations revealed in situ formation of an iron-dihydride complex [H2Fe(CO)(2)(PPh3)(2)] (A) as an active catalytic species. This finding was further supported by cyclic voltammetry investigations and intermediacy of an Fe(0)-Fe(II) species was established. Combined experimental and computational investigations support the existence of an iron-dihydride as the catalyst resting state, which then follows a Fe(II) based catalytic cycle to produce aldehyde.

}, issn = {0002-7863}, doi = {10.1021/jacs.8b01286}, author = {Pandey, Swechchha and Raj, K. Vipin and Shinde, Dinesh R. and Vanka, Kumar and Kashyap, Varchaswal and Kurungot, Sreekumar and Vinod, C. P. and Chikkali, Samir H.} } @article {46348, title = {Imidazole-linked crystalline two-dimensional polymer with ultrahigh proton-conductivity}, journal = {Journal of the American Chemical Society}, volume = {141}, year = {2019}, month = {SEP}, pages = {14950-14954}, type = {Article}, abstract = {

Proton-exchange membrane fuel cells are promising energy devices for a sustainable future due to green features, high power density, and mild operating conditions. A facile proton-conducting membrane plays a pivotal role to boost the efficiency of fuel cells, and hence focused research in this area is highly desirable. Major issues associated with the successful example of Nafion resulted in the search for alternate proton conducting materials. Even though proton carrier loaded crystalline porous organic frameworks have been used for protonconduction, the weak host-guest interactions limited their practical use. Herein, we developed a crystalline 2D-polymer composed of benzimidazole units as the integral part, prepared by the condensation of aryl acid and diamine in polyphosphoric acid medium. The imidazole linked-2D-polymer exhibits ultrahigh proton conductivity (3.2 X 10(-2) S cm(-1)) (at 95\% relative humidity and 95 degrees C) in the pristine state, which is highest among the undoped porous organic frameworks so far reported. The present strategy of a crystalline proton-conducting 2D-polymer will lead to the development of new high performing crystalline solid proton conductor.

}, issn = {0002-7863}, doi = {10.1021/jacs.9b06080}, author = {Ranjeesh, Kayaramkodath Chandran and Ilathvalappil, Rajith and Veer, Sairam Dnyaneshwar and Peter, Joseph and Wakchaure, Vivek Chandrakant and Goudappagouda and Raj, K. Vipin and Kurungot, Sreekumar and Babu, Sukumaran Santhosh} } @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 {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 {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 {48116, title = {Antimicrobial two-dimensional covalent organic nanosheets (2D-CONs) for the fast and highly efficient capture and recovery of phosphate ions from water}, journal = {Journal of Materials Chemistry A}, volume = {10}, year = {2022}, month = {MAR }, pages = {4585-4593}, type = {Article}, abstract = {

The retrieval of depleting resources from wastewater could help resolve the mounting demands for resources in our society. Phosphate is an essential nutrient for all living things. However, the diminution of global reserves of phosphate rock could significantly affect our food security in the near future. At the same time, the removal of phosphates and pathogens is of great importance for water security and de-eutrophication. The specific pH-dependent adsorption and desorption of phosphate ions by water-insoluble adsorbents is an exciting strategy for removing and recovering phosphates from contaminated water. Herein, we report the development of new two-dimensional guanidine-containing covalent organic nanosheets (2D-gCONs). This water-insoluble amorphous polymer (exfoliated) selectively sequestered phosphate ions in the presence of other competing anions and could be reused for multiple cycles. The polymer showed a fast removal of phosphate ions with a maximum adsorption capacity of 398 mg g(-1) (pH 7.0). The sequestered phosphate ions could be easily reclaimed, and the polymer could be recycled just by altering the pH (similar to 10.0) of the aqueous solution. The guanidinium moieties played a pivotal role in exfoliation in aqueous medium and in the antibacterial activities against Gram-negative and Gram-positive bacteria. We hypothesize that the current study may advance the design of water-insoluble CONs to remove and recover phosphate ions from wastewater and could help alleviate the negative impact of water eutrophication. This strategy can also be tweaked to address other severe environmental challenges.

}, issn = {2050-7488}, doi = {10.1039/d1ta10911a}, author = {Dey, Subhasis and Das, Sribash and Patel, Anjali and Raj, K. Vipin and Vanka, Kumar and Manna, Debasis} } @article {47899, title = {Mechanistically guided one pot synthesis of phosphine-phosphite and its implication in asymmetric hydrogenation}, journal = {European Journal of Organic Chemistry}, volume = {2022}, year = {2022}, month = {JAN}, pages = {e202101447}, type = {Article}, abstract = {

Although hybrid bidentate ligands are known to yield highly enantioselective products in asymmetric hydrogenation (AH), synthesis of these ligands is an arduous process. Herein, a one pot, atom-economic synthesis of a hybrid phosphine-phosphite (L1) is reported. After understanding the reactivity difference between an 0-nucleophile versus C-nucleophile, one pot synthesis of Senphos (L1) was achieved (72\%). When L1 was treated with [Rh], P-31 NMR revealed bidentate coordination to Rh. Senphos, in the presence of rhodium, catalyzes the AH of Methyl-2-acetamido-3-phenylacrylate and discloses an unprecedented turn over frequency of 2289, along with excellent enantio-selectivity (92\%). The generality is demonstrated by hydrogenating an array of alkenes. The AH operates under mild conditions of 1-2 bar H-2 pressure, at room temperature. The practical relevance of Ll is demonstrated by scaling-up the reaction to 1 g and by synthesizing DOPA, a drug widely employed for the treatment of Parkinson{\textquoteright}s disease. Computational insights indicate that the R isomer is preferred by 3.8 kcal/mol over the S isomer.

}, keywords = {asymmetric hydrogenation, catalysis, DOPA synthesis, One pot synthesis, Phosphine-phosphite ligand}, issn = {1434-193X}, doi = {10.1002/ejoc.202101447}, author = {Sen, Anirban and Kumar, Rohit and Pandey, Swechchha and Raj, K. Vipin and Kumar, Pawan and Vanka, Kumar and Chikkali, Samir H.} } @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 {48470, title = {Potential role of lewis acid-base adducts in enhancing stereoselectivity in ziegler-natta catalysts: a DFT study}, journal = {Journal of Physical Chemistry C}, volume = {127}, year = {2023}, month = {APR}, pages = {7220-7229}, type = {Article}, abstract = {

Ziegler-Natta (Z-N) systems have been well established as heterogeneous catalysts that produce isotactic polypropylene and polyethylene with great efficiency. Such systems benefit considerably from donors (Lewis bases), whose addition significantly improves the stereoselectivity of polymerization. There is a consensus that the primary role of the external donors is to coordinate at the vacant site created by the extraction of internal donors and thus maintain the stereoselectivity. However, the bite difference between internal donors such as phthalates or succinate derivatives and external donors such as alkoxysilanes raises the question of how external donors can effectively replace internal donors. In order to investigate this, we have chosen four external alkoxysilane donors: (1) diisopropyl dimethoxysilane, (2) dicyclopentyl dimethoxysilane, (3) disec-butyl dimethoxysilane, and (4) sec-butyl(methyl) dimethoxysilane. DFT studies reveal that the bite difference problem can be overcome by the favorable formation of adducts between the alkoxysilane external donors and AlEt2Cl in the Z-N systems. These adducts tend to coordinate in the vicinity of the active site. Furthermore, our findings demonstrate the potential of these Lewis acid-base adducts to enhance the stereoselectivity of Z-N catalysts significantly.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.3c00814}, author = {Raj, K. Vipin and Gupta, Virendra Kumar and Vanka, Kumar} } @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.} }