Redistribution of Trialkyl Silanes Catalyzed by Iridium Silyl Complexes

[Ir(COE)(2)Cl](2) reacts with Et3SiH at 23 degrees C to form a binuclear iridium complex (Et3Si)(2)(H)(2)Ir(mu-Cl)(2)Ir-(H)(2)(SiEt3)(2), 1. Complex 1 reacts further with Et3SiH at 60 degrees degrees C to form a second binuclear iridium complex, Et3Si(H)(2)Ir(mu-SiEt2)(2)Ir(H)(2)SiEt3, 2, containing bridging Et2Si groups. Activation of 2 with H-2 produces trace quantities of a very highly reactive but unobservable species which rapidly and efficiently catalyzes alkyl redistribution reactions of silanes, RRRSiH. D-2 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.