Heterobimetallic Gold/Ruthenium Complexes Synthesized via Post-functionalization and Applied in Dual Photoredox Gold Catalysis.

The synthesis of heterobimetallic Au I /Ru II complexes of the general formula syn- and anti-[{AuCl}(L1∩L2){Ru(bpy) 2 }][PF 6 ] 2 is reported. The ditopic bridging ligand L1∩L2 refers to a P,N hybrid ligand composed of phosphine and bipyridine substructures, which was obtained via a post-functionalization strategy based on Diels-Alder reaction between a phosphole and a maleimide moiety. It was found that the stereochemistry at the phosphorus atom of the resulting 7-phosphanorbornene backbone can be controlled by executing the metal coordination and the cycloaddition reaction in a different order. All precursors, as well as the mono- and multimetallic complexes, were isolated and fully characterized by various spectroscopic methods such as NMR, IR, and UV-vis spectroscopy as well as cyclic voltammetry. Photophysical measurements show efficient phosphorescence for the investigated monometallic complex anti-[(L1∩L2){Ru(bpy) 2 }][PF 6 ] 2 and the bimetallic analogue syn-[{AuCl}(L1∩L2){Ru(bpy) 2 }][PF 6 ] 2 , thus indicating a small influence of the {AuCl} fragment on the photoluminescence properties. The heterobimetallic Au I /Ru II complexes syn- and anti-[{AuCl}(L1∩L2){Ru(bpy) 2 }][PF 6 ] 2 are both active catalysts in the P-arylation of aryldiazonium salts promoted by visible light with H-phosphonate affording arylphosphonates in yields of up to 91 %. Both dinuclear complexes outperform their monometallic counterparts.