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

The crystal structure of bis[-(1,3-dimesityl-1H-imidazol-3-ium-2-yl)methanolato- 2O:O]bis[dichloridocopper(II)], [Cu2Cl4(C22H26N2O)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 Cu2O2 central core with the O atoms bridging between the CuII atoms and thus Z0 = 0.5. The copper centres are further ligated by two chloride ligands, resulting in the CuII 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 Cu2O2 motif. The complex displays C—H Cl interactions involving the H atoms of the heterocycle backbone and the chloride ligands of a neighbouring molecule.