Cooperative Catalysis: Large Rate Enhancements with Bimetallic Rhodium Complexes

A large increase in reaction rate was observed for the catalyzed mono- and dihydroalkoxylation of alkynes when structurally constrained bimetallic Rh­(I) catalysts with imidazolyl-imine ligands were compared to their monometallic analogues. The “cooperative” enhancement was vastly improved by restricting the conformational freedom of the bimetallic structure and minimizing the intermetallic Rh···Rh distance.