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

Abstract

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 (B 2 (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 B 2 (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.

Aluminum-Containing Heterobimetallic Complexes as Versatile Platforms for Homogeneous Catalysis

“…The plausible reaction mechanism involves cooperative cleavage of the C­(sp 2 )–O bond at the Rh–Al bond, similar to the previously disclosed C–F bond activation (Figure ). An extensive density functional theory study of the mechanism matches the experimental observations . Moreover, hydrosilane Si–H bond activation and arene/aryl-Bpin reduction elimination occur at the Rh center alone.…”