Crystal structure of the [(1,3-dimesityl-1H-imidazol-3-ium-2-yl)methano­lato]copper(II) chloride dimer: insertion of formaldehyde into a copper–carbene bond

The crystal structure of bis­[μ-(1,3-dimesityl-1H-imidazol-3-ium-2-yl)methano­lato-κ(2) O:O]bis­[di­chlorido­copper(II)], [Cu(2)Cl(4)(C(22)H(26)N(2)O)(2)], is reported. The complex is assumed to have formed via the insertion of formaldehyde into the copper–carbon bond in an N-heterocyclic carbene complex of copper(I) chloride. The structure of the binuclear mol­ecule possesses a crystallographic­ally centrosymmetric Cu(2)O(2) central core with the O atoms bridging between the Cu(II) atoms and thus Z′ = 0.5. The copper centres are further ligated by two chloride ligands, resulting in the Cu(II) atoms residing in a distorted square-planar environment. The Cu—O bond lengths are shorter than those previously reported in structures with the same central Cu(2)O(2) motif. The complex displays C—H⋯Cl inter­actions involving the H atoms of the heterocycle backbone and the chloride ligands of a neighbouring mol­ecule.