Diruthenium Carbido Complexes as N‑Heterocyclic Carbene Like C‑Donor Ligands to Group 11 Metals

Deprotonation of the diruthenium μ-methylidyne complex [(Cp*Ru)2(μ-NtBu)­(μ-CH)]­[BF4] (Cp* = η5-C5Me5) with 2 equiv of KN­(SiMe3)2 in the presence of CuCN, AgOTf, or AuCl­(SMe2) afforded the trigonal planar bridging carbido complexes [(Cp*Ru)2(μ-NtBu)­(μ3-C)­M­{N­(SiMe3)2}] (M = Cu (4), Ag (5), and Au (6)). Complexes 4 and 6 were characterized crystallographically. The M–C bonding in these complexes showed considerable similarity with that in the N-heterocyclic carbene (NHC) derivatives (NHC)­M­{N­(SiMe3)2} (M = Cu and Au), illustrating the analogy between the diruthenium carbido ligand [(Cp*Ru)2(μ-NtBu)­(μ-C)] and NHCs. The reaction of 4 with 2,6-di-tert-butylphenol allowed derivatization via protonolytic exchange of the disilazide moiety, yielding the aryloxo complex [(Cp*Ru)2(μ-NtBu)­(μ3-C)­Cu­(OAr)] (7; Ar = 2,6-tBu2C6H3), which was also structurally characterized. The electron donor ability and steric bulkiness of the diruthenium carbido ligand were studied by computational methods.