Preparation and reactions of some neutral pentamethylcyclopentadienylruthenium vinylidene complexes

Abstract

A synthesis of neutral vinylideneruthenium complexes [RuCl(CCHR)(PPh₃)(η-C₅Me₅)] (R = Ph, Bu^t or SiMe₃) from [RuCl(PPh₃)₂(η-C₅Me₅)] and 1-alkynes has been developed. This takes advantage of the presence of two bulky ligands (PPh₃ and C₅Me₅), which results in displacement of one PPh₃ ligand (rather than chloride) and concomitant isomerisation of the 1-alkyne to vinylidene ligands. The vinylidene complexes undergo facile loss of HCl on treatment with NaOMe in the presence of a 2e donor ligand (L) to give the neutral acetylide complexes [Ru(CCR)L(PPh₃)(η-C₅Me₅)] [R = Ph, L = PPh₃, CO, O₂ or dppm-P; R = Bu^t, L = PPh₃, CO, C₂H₄, dppe-P, C₂(PPh₂)₂-P, S₂, P(OMe)₃ or AsPh₃]; the complexes [Ru(CCBu^t)(L₂)(η-C₅Me₅)] [L₂ = dppm or PPh₂CH CHPPh₂] and [Ru(S₂CCCBu^t)(PPh₃)(η-C₅Me₅)] were also obtained. Crystal structure determinations were carried out on eleven of the complexes.