Bimetallic Pd(III) complexes in palladium-catalysed carbon–heteroatom bond formation.

Palladium is a common transition metal for catalysis, and the fundamental organometallic reactivity of palladium in its 0, I, II and IV oxidation states is well established. The potential role of Pd(III) in catalysis has not been investigated because organometallic reactions that involve Pd(III) have not been reported previously. In this article we present the formation of carbon–heteroatom bonds from discrete bimetallic Pd(III) complexes and show the synergistic involvement of two palladium atoms of the bimetallic core during both oxidation and reductive elimination. Our results challenge the currently accepted mechanism for oxidative palladium catalysis via Pd(II)–Pd(IV) redox cycles and implicate bimetallic palladium complexes in redox catalysis. The new mechanistic insight provides an opportunity to explore rationally the potential of bimetallic palladium catalysis for synthesis.