Synthesis of bimetallic rhodium phosphinine complexes with enhanced catalytic activity towards alkyne hydrosilylation

Reaction of alkynes with PC carbene P complex 1 (featuring an alkylidene anchored pincer ligand) results in the formation of 773 -benzo- A.5 -phosphinine rhodium complexes 2 . Reacting two equivalents of 1 with diynes allows easy access to bimetallic 773 -benzo- A.5 -phosphinine rhodium complexes 3 . Using this approach, compounds 2a-c,e and 3a-c are synthesized and characterized. Testing these compounds as catalysts in the hydrosilylation of alkynes reveals that bimetallic complexes 3a-c show enhanced activity to monometallic and monocationic analogues (i.e. 2d ) with improved yields of up to 13 times and reaction rates of over 4 times for the same rhodium concentration. We show that the dicationic monometallic 773 benzo- A.5 -phosphinine rhodium complex 2e also displays enhanced activity and that the higher activity in bimetallic complexes 3a-c likely arises from their dicationic nature. (c) 2023 Elsevier B.V. All rights reserved.