Heterobimetallic Coinage Metal‐Ruthenium Complexes Supported by Anionic N‐Heterocyclic Carbenes

The lithium complexes [(WCA‐NHC)Li(toluene)] of anionic N‐heterocyclic carbenes with a weakly coordinating borate moiety (WCA‐NHC, WCA=B(C6F5)3, NHC=IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) were used for the preparation of silver(I) or copper(I) WCA‐NHC complexes. While the reactions in THF with AgCl or CuCl afforded anionic mono‐ and dicarbene complexes with solvated lithium counterions [Li(THF)n]+ (n=3, 4), the reactions in toluene proceeded with elimination of LiCl and formation of the neutral phosphine and arene complexes [(WCA‐NHC)M(PPh3)] and [(WCA‐NHC)M(η2‐toluene)] (M=Ag, Cu). The latter were used for the preparation of chlorido‐ and iodido‐bridged heterobimetallic Ag/Ru and Cu/Ru complexes [(WCA‐NHC)M(μ‐X)2Ru(PPh3)(η6‐p‐cymene)] (M=Ag, Cu, X=Cl; M=Ag, X=I). Surprisingly, these complexes resisted the elimination of CuCl, AgCl, or AgI, precluding WCA‐NHC transmetalation. Silver(I) and copper(I) arene complexes [(WCA‐NHC)M(η2‐toluene)] (M=Ag, Cu) with a weakly coordinating anionic (WCA) borate moiety were prepared and their ability to serve as transmetalation reagents was investigated. However, the high stability of WCA‐NHC‐metal bonds provided access to heterobimetallic complexes such as [(WCA‐NHC)M(μ‐Cl)2Ru(PPh3)(η6‐p‐cymene)], which resisted the elimination of AgCl or CuCl, respectively.