@article {42758, title = {Ruthenium(II), copper(I) and silver(I) complexes of large bite bisphosphinite, bis(2-diphenylphosphinoxynaphthalen-1-yl)methane: Application of Ru(II) complexes towards the hydrogenation of styrene and phenylacetylene}, journal = {Journal of Organometallic Chemistry}, volume = {691}, year = {2006}, month = {JUL}, pages = {4265{\textendash}4272}, type = {Article}, abstract = {

Ruthenium(II), copper(I) and silver(I) complexes of large bite bisphosphinite Ph2P{(-OC10H6)(μ-CH2)(C10H6O-)}PPh2 (1) are described. Reactions of bisphosphinite 1 with [Ru(η6-p-cymene)(μ-Cl)Cl]2 and RuCl2(PPh3)3 afford mono- and bis-chelate complexes [RuCl(η6-p-cymene){η2-Ph2P{(-OC10H6)(μ-CH2)(C10H6O-)}PPh2-κP,κP}]Cl (2) and trans-[RuCl2{η2-Ph2P{(-OC10H6)(μ-CH2)(C10H6O-)}PPh2-κP,κP}2] (3), respectively. Treatment of 1 with CuX (X = Cl, Br and I) furnish 10-membered chelate complexes of the type [Cu(X){η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}] (4, X = Cl; 5, X = Br; 6, X = I), whereas [Cu(MeCN)4]PF6 affords a bis-chelated cationic complex [Cu{η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}2][PF6] (7). Reaction between 1 and AgOTf produce both mono- and bis-chelated complexes [Ag{η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}(SO3CF3)] (8) and [Ag{η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}2][SO3CF3] (9), respectively; whereas the similar reaction of 1 with[Ag(OTf)PPh3] affords chelate complex of the type [Ag{η2-Ph2P(-OC10H6)(μ-CH2)(C10H6O-)PPh2-κP,κP}(PPh3)(SO3CF3)] (10). All the complexes were characterized by 1H NMR, 31P NMR, elemental analysis and mass spectrometry, including low-temperature NMR studies in the case of silver complexes. The molecular structures of 4 and 6 are determined by X-ray diffraction studies. Ruthenium complexes 2 and 3 promote catalytic hydrogenation of styrene and phenylacetylene with good turnover numbers.

}, doi = {10.1016/j.jorganchem.2006.06.040}, author = {Punji, Benudhar and Mague, Joel T. and Balakrishna, Maravanji S.} } @article {42741, title = {Rational design of highly active {\textquotedblleft}hybrid{\textquotedblright} phosphine-phosphinite pincer iridium catalysts for alkane metathesis}, journal = {ACS Catalysis}, volume = {3}, year = {2013}, month = {SEP}, pages = {2505{\textendash}2514}, abstract = {

Both the bisphosphine and bisphosphinite pincer complexes (tBu4PCP)IrH2 and (tBu4POCOP)IrH2 can cocatalyze alkane metathesis in tandem with olefin metathesis catalysts, but the two complexes have different resting states during catalysis, suggesting that different steps are turnover-limiting in each case. This led to the hypothesis that a complex with intermediate properties would be catalytically more active than either of these two species. Accordingly, {\textquotedblleft}hybrid{\textquotedblright} phosphine{\textendash}phosphinite pincer ligands (PCOP) and the corresponding iridium complexes were synthesized (3c{\textendash}e). In tandem with olefin-metathesis catalyst MoF12, (tBu4PCOP)IrH2 displays significantly higher activity for the metathesis of n-hexane than does (tBu4PCP)IrH2 or (tBu4POCOP)IrH2. (tBu2PCOPiPr2)IrH4 (3d) is even more active (\>30-fold more active than (tBu4POCOP)IrH2) and affords nearly 4.6 M alkane products after 8 h at 125 {\textdegree}C.

}, doi = {10.1021/cs400624c}, author = {Nawara-Hultzsch, Agnieszka J. and Hackenberg, Jason D. and Punji, Benudhar and Supplee, Carolyn and Emge, Thomas J. and Bailey, Brad C. and Schrock, Richard R. and Brookhart, Maurice and Goldman, Alan S.} } @article {42740, title = {Recent advances in transition-metal-free direct C{\textendash}C and C{\textendash}heteroatom bond forming reactions}, journal = {RSC Advances}, volume = {3}, year = {2013}, month = {APR}, pages = {11957-11986}, abstract = {

The efficient generation of biaryl compounds and heterocycles via the advent of the transition-metal-free coupling reaction constitutes an important development in the last few years. Although early methods for the construction of such molecules involved transition metals, recent advances in the field have witnessed a myriad of elegant reports without the use of metal sources. The serendipitous discovery and observation of synthetic chemists have realized that there lies a great potential in exploiting the inherent reactivity of molecules in absence of transition metal. The key to the success of such coupling reactions is the use of a strong base, oxidant and a catalytic amount of N-donor ligands which contribute significantly. This review aims to highlight the recent progress in the field of transition-metal-free direct C{\textendash}C and C{\textendash}heteroatom bond forming reactions via the use of a strong base and (or) an oxidant.

}, doi = {10.1039/C3RA40813B}, author = {Mehta, Vaibhav P. and Punji, Benudhar} } @article {48102, title = {Room temperature chemoselective hydrogenation of C=C, C=O and C=N bonds by using a well-defined mixed donor Mn(I) pincer catalyst}, journal = {Chemical Science}, volume = {13}, year = {2022}, month = {NOV }, pages = {13764-13773}, type = {Article}, abstract = {

Chemoselective hydrogenation of C=C, C=O and C=N bonds in alpha,beta-unsaturated ketones, aldehydes and imines is accomplished at room temperature (27 degrees C) using a well-defined Mn(I) catalyst and 5.0 bar H-2. Amongst the three mixed-donor Mn(I) complexes developed, kappa(3)-((PNNPyz)-P-R2-N-3)Mn(CO)(2)Br (R = Ph, Pr-i, Bu-t); the Bu-t -substituted complex ((PNNPyz)-P-tBu2-N-3)Mn(CO)(2)Br shows exceptional chemoselective catalytic reduction of unsaturated bonds. This hydrogenation protocol tolerates a range of highly susceptible functionalities, such as halides (-F, -Cl, -Br, and -I), alkoxy and hydroxy, including hydrogen-sensitive moieties like acetyl, nitrile, nitro, epoxide, and unconjugated alkenyl and alkynyl groups. Additionally, the disclosed method applies to indole, pyrrole, furan, thiophene, and pyridine-containing unsaturated ketones leading to the corresponding saturated ketones. The C=C bond is chemoselectively hydrogenated in alpha,beta-unsaturated ketones, while the aldehyde{\textquoteright}s C=O bond and imine{\textquoteright}s C=N bond are preferentially reduced over the C=C bond. A detailed mechanistic study highlighted the non-innocent behavior of the ligand in the ((PNNPyz)-P-tBu2-N-3) Mn(I) complex and indicated a metal-ligand cooperative catalytic pathway. The molecular hydrogen (H-2) acts as a hydride source, whereas MeOH provides a proton for hydrogenation. DFT energy calculations supported the facile progress of most catalytic steps, involving a crucial turnover-limiting H-2 activation.

}, issn = {2041-6520}, doi = {10.1039/d2sc05274a}, author = {Shabade, Anand B. and Sharma, Dipesh M. and Bajpai, Priyam and Gonnade, Rajesh G. and Vanka, Kumar and Punji, Benudhar} } @article {48118, title = {Room temperature Z-selective hydrogenation of alkynes by hemilabile and non-innocent (NNN)Co(ii) catalysts}, journal = {Catalysis Science \& Technology}, volume = {12}, year = {2022}, month = {MAR }, pages = {1843-1849}, type = {Article}, abstract = {

Hemilabile and phosphine-free quinolinyl-based NNN-type pincer and non-pincer cobalt complexes were developed for the room temperature catalytic transfer semi-hydrogenation of alkynes to Z-alkenes. Treatment of the quinolinyl-amine ligand, [C9H6N(NH)CH2CH2NEt2] ((NNN2NEt2)-N-Q-N-CH)-H with CoX2 afforded the pincer complexes kappa(3)-((NNN2NEt2)-N-Q-N-CH)CoX2 (X = Cl, Br), whereas, the quinolinyl-amide ligand, [C9H6N(NH)C(O)CH2NEt2] ((NNNNEt2)-N-Q-N-C(O))-H gave chelate anionic complexes kappa(2)-((NN)-N-Q)CoX2((NHNEt2)-H-C(O)) (X = Cl, Br). The well-defined anionic non-pincer cobalt complexes efficiently catalyzed the semi-hydrogenation of diverse alkynes to deliver highly chemoselective and stereodivergent Z-alkenes at room temperature. This hydrogenation exhibited broad substrate scope with the tolerance of sensitive functional groups, such as -Cl, -Br, -I, -OH, -NH2, -COOMe, and pyridinyl, employing a stable and user-friendly ammonia borane hydrogen source.

}, issn = {2044-4753}, doi = {10.1039/d2cy00027j}, author = {Sharma, Dipesh M. and Gouda, Chandrakant and Gonnade, Rajesh G. and Punji, Benudhar} }