Non-Metal Catalyzed Heterodehydrocoupling of Phosphines and Hydrosilanes: Mechanistic Studies of B(C6F5)3-Mediated Formation of P-Si Bonds

Lipeng Wu, Saurabh Chitnis, Haijun Jiao, Vincent Annibale, Ian Manners

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Abstract

Non-metal catalysed heterodehydrocoupling of primary and secondary phosphines (R1R2PH, R2 = H or R1) with hydrosilanes (R1’R2’R3’SiH, R2’, R3’ = H or R1’) to produce synthetically useful silylphosphanes (R1R2P-SiR1’R2’R3’) has been achieved using B(C6F5)3 as the catalyst (10 mol%, 100 oC). Kinetic studies demonstrated that the reaction is first-order in silane and B(C6F5)3 but zero-order in phosphine. Control experiments, DFT calculations as well as DOSY NMR studies suggest that a R1R2HP•B(C6F5)3 adduct is initially formed and which subsequently undergoes partial dissociation to form an “encounter complex” held together via weak secondary interactions. The latter mediates Frustrated Lewis Pair-type Si-H bond activation of the silane substrates. We also found that B(C6F5)3 catalyses the homodehydrocoupling of primary phosphines to form cyclic phosphine rings and the first example of catalytic hydrosilylation of P-P bonds to produce silylphosphanes (R1R2P-SiR1’R2’R3’). Moreover, the introduction of PhCN to the reactions involving secondary phosphines with hydrosilanes allowed the heterodehydrocoupling reaction to proceed efficiently under much milder conditions (1.0 mol% B(C6F5)3 at 25 °C). Mechanistic studies, as well as DFT calculations, revealed that PhCN plays a key mechanistic role in facilitating the dehydrocoupling reactions rather than simply functioning as H2-acceptor.
Original languageEnglish
Pages (from-to)16780-16790
Number of pages11
JournalJournal of the American Chemical Society
Volume139
Issue number46
Early online date9 Oct 2017
Publication statusPublished - 22 Nov 2017

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