Nucleophilic cyclocarbenes as ligands in metal halides and metal oxides

The nucleophilic cyclocarbene 1,3-dimethylimidazolin-2-ylidene (1) reveals universal ligand properties in metal coordination chemistry: in addition to the well-known stabilization of low oxidation-state transition metal fragments, this particular class of carbenes also coordinates with metal halides and metal oxides thus resembling the properties of conventional ether (O), amine (N), and phosphane (P) ligands. Complexes of titanium(IV), zirconium(IV), hafnium(IV), vanadium(II), niobium(IV), tantalum(IV) of general formula MX_nL_m (3a–f) and the rhenium(VII) of formula CH₃ReO₃L₂ (3g) are reported (L = 1,3-dimethylimidazolin-2-ylidene).