Reactions of (imidazol-2-ylidene)silver(I) chlorides with group 4 metal containing Lewis acids

The reactivity of the monomeric N-heterocyclic carbene silver(I) complexes, 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene-silver(I) chloride ([Ag(IMes)Cl], 1) and 1,3-bis-(4-bromo-2,6-dimethylphenyl)imidazol-2-ylidene-silver(I) chloride ([Ag(IMeSBr)Cl], 2), toward the group 4 metal containing Lewis acids, TiCl4 and (eta(5)-C5H5)ZrCl3](-) in dichloromethane was investigated. Instead of the expected transfer of the A-heterocyclic carbene to the Lewis acidic metal centers with accompanying precipitation of AgCl, chloride transfer occurred leading to the formation of the salts, [Ag(IMeS)(2)](+)[(TiCl3)(2)(mu(2)-Cl)(3)](-)(_) (3) and [Ag(IMes(Br))(2)(+)[{(eta(5)-C5H5)ZrCl}(2)(mu(2)-Cl)(3)(-) (4). The structure of the [Ag(IMes(Br))(2)](+) cation in 4 is significantly distorted in the solid state by interactions between the para-Br atoms of the IMeSBr ligands and chloride ligands of the anions.