A family of rhodium(i) NHC chelates featuring O-containing tethers for catalytic tandem alkene isomerization–hydrosilylation. Issue 3 (25th November 2020) - Srivastava, Ravi
Abstract : The catalytic performances in hydrosilylation of alkenes strongly depend on the structure of O-functionalized NHC Rh(i ) complexes. Abstract : The rhodium complex Rh(HL)(COD)Cl, 1, L being a functionalized N-heterocyclic carbene (NHC) ligand with an oxygen-containing pendant arm, has been used as the entry point to synthesize a series of neutral and cationic Rh(i ) O, C chelates. While the Rh–carbene interaction is similar in all these 16-electron complexes, structural analysis reveals that the strength of the Rh–O bond is greatly affected by the nature of the O-donor: R-O − > R-OH > R-OBF3 . These subtle changes in the nature of the O-containing tether are found to be responsible for large differences in the alkene hydrosilylation catalytic activity of these compounds: the stronger the Rh–O interaction, the better the catalytic performances. The most active catalyst, [Rh(L)(COD)], 2, demonstrated good catalytic activity under mild reaction conditions for the hydrosilylation of a range of alkene substrates with the industrially relevant non-activated tertiary silane, 1, 1, 1, 3, 5, 5, 5-heptamethyltrisiloxane (MD H M). Furthermore, this complex is an effective catalyst for the selective remote functionalization of internal olefins at room temperature via tandem alkene isomerization–hydrosilylation.