HOMOLEPTIC CARBENE SILVER(I) AND CARBENE COPPER(I) COMPLEXES

The syntheses and characterizations of homoleptic bis(carbene) adducts of Ag(I) and Cu(I) are described. These carbene adducts are available directly from the reaction of the stable nucleophilic carbene 1,3-dimesitylimidazol-2-ylidene and the corresponding metal triflate. NMR data are consistent with the bis(carbene)metal structures and suggest a level of delocalization in the imidazole ring that is intermediate between those of the free carbene and imidazolium ions. The X-ray crystal structure of the silver-carbene adduct is reported: [C42H48N4Ag]CF3-SO3, monoclinic, space group P2(1)/c (No. 14), a = 1167.5(l) pm, b = 1472.9(2) pm, c = 2479.8(2) pm, beta = 95.31(1)-degrees; T = -70-degrees-C, Z = 4. The silver is essentially linearly coordinated with the imidazole rings twisted 39.7-degrees relative to one another. The solid-state structure of the silver-carbene adduct is compared with those of related gold-carbene adducts.