Synthesis and Characterization of Heterobimetallic Complexes with Direct Cu–M Bonds (M = Cr, Mn, Co, Mo, Ru, W) Supported by N‑Heterocyclic Carbene Ligands: A Toolkit for Catalytic Reaction Discovery

Building upon the precedent of catalytically active (NHC)­Cu–FeCp­(CO)2 complexes, a series of (NHC)­Cu–[M] complexes were synthesized via the addition of Na+[M]− reagents to (NHC)­CuCl synthons. The different [M]− anions used span a range of 7 × 107 relative nucleophilicity units, allowing for controlled variation of nucleophile/electrophile pairing in the heterobimetallic species. Direct Cu–M bonds (M = Cr, Mn, Co, Mo, Ru, W) formed readily when the bulky IPr carbene was used as a support. Crystallographic characterization and computational examination of these complexes was conducted. For the smaller IMes carbene, structural isomerism was observed when using the weakest [M]− nucleophiles, with (IMes)­Cu–[M] and {(IMes)2Cu}­{Cu­[M]2} isomers being observed in equilibrium. Collectively, the series of complexes provides a toolbox for catalytic reaction discovery with precise control of structure–function relationships.