Simple, direct synthesis and structure of hexa-μ-chloro-tetrakis(1-methylimidazole)-μ4-oxo-tetracopper(II)

Cu4C160(C4H6N2)4) , M r = 811"32, ortho- rhombic, Pbca, a = 18.985 (7), b = 33.197 (7), c = 18.917(5) A, V=l1922(6) A 3, Z=16, Om=l"80, Dx = 1"81 g cm -3, h.(Cu Ka)= 1"5418/1, Iz = 84"2 cm-~, F(000) = 6432, T = 293 K, R = 0.051 for 6860 reflections with Fo ~ 40(Fo). (Cu4f|60- (1-Melm)4) is readily synthesized by simply mixing concentrated methanolic solutions of copper(II) chloride hydrate and 1-methylimidazole under ambi- ent conditions. Each of the two molecules in the asymmetric unit consists of a #4-O atom surrounded by a tetrahedron of Cu atoms with /x2-Cl atoms bridging between the Cu atoms, and with 1- methylimidazole completing the distorted trigonal bipyramidal coordination around the Cu atoms. The average Cu--O bond distance is 1.902 (7)A while the average Cu--C1 bond length is 2.417(30)A. Deviations of the coordination polyhedron from ideal trigonal bipyramidal symmetry in this and related compounds are also examined.