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.