Redistribution of Trialkyl Silanes Catalyzed by Iridium Silyl Complexes

Abstract

[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.