Dinuclear Influence on the Mechanism, Reactivity, and Selectivity During Rh–Al-Catalyzed Aryl Ether C–O Bond Reduction/Defunctionalization

Dinuclear metal complexes with a direct metal–metal interaction have the potential for unique mechanisms, intermediates, and selectivity during catalysis. Here, we report density functional theory calculations that directly evaluate the influence of a dinuclear metal–metal interaction during aryl C–O bond reduction/defunctionalization with either hydrosilane or bis(pinacolato)diboron (B2(pin)2) reagents catalyzed by a heterodinuclear Rh–Al complex. Our calculations demonstrate the critical Rh–Al cooperative behavior necessary for aryl C–O bond activation and catalytic turnover. However, only the Rh metal center is involved in hydrosilane Si–H bond activation to generate a defunctionalized arene or B–B bond activation of B2(pin)2 to form an aryl boronic acid pinacol ester. The calculations also reveal an unanticipated very strong ligand-to-substrate steric effect that controls reduction site selectivity.