Si-H and Si-C bond cleavage reactions of silane and phenylsilanes with Mo(PMe3)6: silyl, hypervalent silyl, silane, and disilane complexes.

Mo(PMe3)6 cleaves the Si-H bonds of SiH4, PhSiH3, and Ph2SiH2 to afford a variety of novel silyl, hypervalent silyl, silane, and disilane complexes, as respectively illustrated by Mo(PMe3)4(SiH3)2H2, Mo(PMe3)4(κ(2)-H2-H2SiPh2H)H, Mo(PMe3)3(σ-HSiHPh2)H4, and Mo(PMe3)3(κ(2)-H2-H2Si2Ph4)H2. Mo(PMe3)4(κ(2)-H2-H2SiPh2H)H and Mo(PMe3)3(κ(2)-H2-H2Si2Ph4)H2 are respectively the first examples of complexes that feature a hypervalent κ(2)-H2-H2SiPh2H silyl ligand and a chelating disilane ligand, and both compounds convert to the diphenylsilane adduct, Mo(PMe3)3(σ-HSiHPh2)H4, in the presence of H2. Mo(PMe3)4(SiH3)2H2 undergoes isotope exchange with SiD4, and NMR spectroscopic analysis of the SiHxD4-x isotopologues released indicates that the reaction does not occur via initial reductive elimination of SiH4, but rather by a metathesis pathway.