Catalytic hydrosilylation of acetylenes mediated by phosphine complexes of cobalt(I), rhodium(I), and iridium(I)

The complexes [Co(PPh3)3Cl] (1), [Co(PPh3)2(CO)2Cl] (2), [Co(PMe3)3Cl] (3), [Co(PMe3)2(CO)2Cl] (4), [Rh(dppe)(CO)Cl] (5), [Rh(PPh2Me)2(CO)Cl] (6), [Ir(dppe)(CO)Br] (7), and [Ir(PPh2Me)2(CO)Cl] (8) catalyse the hydrosilylation of a range of acetylenes including 1-hexyne, phenylacetylene, and 1-phenyl-1-propyne with triethylsilane. In the case of 1-hexyne and 1-phenyl-1-propyne, only the expected hydrosilylation products were observed; however, when the substrate was phenylacetylene, cyclotrimerisation and dimerisation products were observed in addition to the expected vinylsilanes. No hydrosilation was observed with alkene substrates; however, in the presence of some metal complexes, there was double bond migration and cis/trans-isomerisation probably mediated by the formation of metal hydrides in the reaction mixture.