Hydrosilylation of alkynes mediated by N-heterocyclic carbene platinum(0) complexes

The hydrosilylation of terminal alkynes by silanes catalyzed by N-heterocyclic carbene platinum(O) complexes has been investigated. The alkynes included 1-octyne and phenylacetylene. The silanes investigated were bis(trimethylsilyloxy)methylsitane, (trimethylsilyloxy)dimethylsilane, tert-butyldimethylsilane, triphenylsilane, phenyldimethylsilane, triethylsilane, and triethoxysilane. X-ray crystal structures for [Pt(N,N'-dicyclohexylimidazol-2-ylidene)(eta(2)-dimethylacetylenedicarboxylate)(2)] (8) and [Pt{C(E)=C(E)-C(E)=C(E)}(N,N'-dimethylbenzimidazol-2-ylidene)(sigma-NCCH3)] (10) (E = CO2Me) have been obtained. A selectivity model, based on structural parameters of the N-heterocyclic carbene, has been devised in order to rationalize the observed regioselectivity obtained. By a judicious choice of catalyst, alkyne, and silane, the regioselectivity of the addition can be controlled.