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Redistribution of Trialkyl Silanes Catalyzed by Iridium Silyl Complexes

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journal contribution
posted on 03.02.2012, 00:00 by Sehoon Park, Bong Gon Kim, Inigo Göttker-Schnetmann, Maurice Brookhart
[Ir­(COE)2Cl]2 reacts with Et3SiH at 23 °C to form a binuclear iridium complex (Et3Si)2(H)2Ir­(μ-Cl)2Ir­(H)2(SiEt3)2, 1. Complex 1 reacts further with Et3SiH at 60 °C to form a second binuclear iridium complex, Et3Si­(H)2Ir­(μ-SiEt2)2Ir­(H)2SiEt3, 2, containing bridging Et2Si groups. Activation of 2 with H2 produces trace quantities of a very highly reactive but unobservable species which rapidly and efficiently catalyzes alkyl redistribution reactions of silanes, RR′R″SiH. D2 and silane exchange experiments establish reactivity features of both 2 and the reactive intermediate. The intermediate cannot be observed, but it is likely a monomeric iridium silyl silylene complex that catalyzes alkyl scrambling via silane exchanges coupled with 1,3-alkyl migrations between silicon centers. DFT calculations support such a mechanism.