Highly Efficient and Reusable Alkyne Hydrosilylation Catalysts Based on Rhodium Complexes Ligated by Imidazolium-Substituted Phosphine

Abstract

Rhodium complexes ligated by imidazolium-substituted phosphine were used as catalysts in the hydrosilylation of alkynes (1-heptyne, 1-octyne, and phenylacetylene) with 1,1,1,3,5,5,5-heptamethyltrisiloxane (HMTS) or triethylsilane (TES). In all cases, the above complexes showed higher activity and selectivity compared to their precursors ([Rh(PPh3)3Cl] and [{Rh(µ-Cl)(cod)}2]). In the reactions with aliphatic alkynes (both when HMTS and TES were used as hydrosilylating agents), β(Z) isomer was mainly formed, but, in the reaction of phenylacetylene with TES, the β(E) product was formed. The catalysts are very durable, stable in air and first and foremost insoluble in the reactants which facilitated their isolation and permitted their multiple use in subsequent catalytic runs. They make a very good alternative to the commonly used homogeneous catalysts.