Assisted Tandem Catalysis with M–M Bonded Heterobimetallic Pd–Pt Complexes: Accessing Both Pd and Pt Catalytic Cycles

Abstract

We report the synthesis of M–M bonded Pd–Pt complexes at the Pd(I)/Pt(I) and Pd(I)/Pt(III) oxidation states. These bimetallic complexes act as a reservoir for catalytically active Pd and Pt centers, and catalysis is observed in a variety of Pd- and Pt-catalyzed reactions. We demonstrate that tandem catalytic reactions with our Pd(I)/Pt(I) complex can capitalize on both Pd and Pt catalytic cycles to enable multistep processes. These include tandem hydrosilylation/Hiyama coupling, Suzuki coupling/amide reduction, Buchwald–Hartwig amination/amide reduction, and Heck coupling/amide reduction. Tandem cycloisomerization/Heck coupling is also observed with our Pd(I)/Pt(III) complex. Control studies demonstrate that homobimetallic Pd–Pd and Pt–Pt complexes do not perform the tandem catalytic reactions and that the Pd–Pt complex is stable under air and moisture for at least 9 months. The M–M bond in these complexes enables access to unique Pd and Pt oxidation states and facilitates M–M communication, both of which can have an impact during catalysis.