Multiple coupling of silanes with imido complexes of Mo.

The bis(imido) complexes ((t)BuN[double bond, length as m-dash])2Mo(PMe3)(L) (L = PMe3, C2H4) react with up to three equivalents of silane PhSiH3 to give the imido-bridged disilyl silyl Mo(vi) complex ((t)BuN){μ-(t)BuN(SiHPh)2}Mo(H)(SiH2Ph)(PMe3)2 (3) studied by NMR, IR and X-ray diffraction. NMR data supported by DFT calculations show that complex 3 is an unusual example of a silyl hydride of Mo(VI), without significant SiH interaction. Mechanistic NMR studies revealed that silane addition proceeds in a stepwise manner via a series of Si-H∙∙∙M agostic and silanimine complexes whose structures were further elucidated by DFT calculations.

Unusual structure, fluxionality, and reaction mechanism of carbonyl hydrosilylation by silyl hydride complex [(ArN=)Mo(H)(SiH2Ph)(PMe3)3].

The reactions of bis(borohydride) complexes [(RN=)Mo(BH4)2(PMe3)2] (4: R = 2,6-Me2C6H3; 5: R = 2,6-iPr2C6H3) with hydrosilanes afford new silyl hydride derivatives [(RN=)Mo(H)(SiR'3)(PMe3)3] (3: R = Ar, R'3 = H2Ph; 8: R = Ar', R'3 = H2Ph; 9: R = Ar, R'3 = (OEt)3; 10: R = Ar, R'3 = HMePh). These compounds can also be conveniently prepared by reacting [(RN=)Mo(H)(Cl)(PMe3)3] with one equivalent of LiBH4 in the presence of a silane. Complex 3 undergoes intramolecular and intermolecular phosphine exchange, as well as exchange between the silyl ligand and the free silane.