Silyl-substituted alkylidenes: preparation of the novel complexes and mechanistic studies of their formation from reactions of alkylidenes with silanes and silyl-to-alkylidyne migration

Alkylidene complexes (Me 3 SiCH 2 ) 3 Ta(PMe 3 )=CHSiMe 3 (1) and Me 3 SiCH 2 Ta(PMe 3 ) 2 (=CHSiMe 3 ) 2 (3a) were found to react with phenylsilanes H 2 SiR'Ph (R' = Me, Ph) and (PhSiH 2 ) 2 CH 2 to give disilyl-substituted alkylidenes (Me 3 SiCH 2 ) 3 Ta=C(SiMe 3 )(SiHR'Ph) (2) and novel metallasilacyclobutadiene and metalladisilacyclohexadiene complexes. Silyl-substituted alkylidene complex (Bu t CH 2 ) 2 W(=O)[=C(But)(SiPh 2 Bu t )] (5a) was prepared from the reaction of O 2 with an equilibrium mixture (Bu t CH 2 )W(=CHBu t ) 2 (SiPh 2 Bu t ) (4b) ⇔ (Bu t CH 2 ) 2 W(≡CBu t )(SiPh 2 Bu t ) (4a). Our recent studies of the preparation of these complexes and mechanistic pathways in the formation of these silyl-substituted alkylidene complexes are summarized.