STRUCTURE OF TETRAKIS(TETRAETHYLAMMONIUM) HEXAKIS(1,1-DICYANOETHYLENE-2,2-DISELENOLATO-SE,SE')OCTACUPRATE

[(C2H5)4N]4[Cu8{Se2C = C(CN)2}6], 4C8H20N+.C24N12Cu8Se12(4-), M(r) = 2433.3, monoclinic, P2(1)/c, a = 14.830 (2), b = 17.690 (3), c = 16.040 (3) angstrom, beta = 100.61 (4)-degrees, V = 4136.0 (7) angstrom 3, Z = 2, D(x) = 1.954 Mg m-3, lambda(Ag K-alpha) = 0.5597 angstrom, mu = 4.68 mm-1, F(000) = 2336, T = 298 K, R = 0.056 for 3844 observed reflections. The title compound is isostructural with the corresponding sulfur ligand compound [(C2H5)4N]4[Cu8{S2C = C(CN)2}6] and consists of a distorted cube of Cu atoms with an average Cu-Cu distance of 2.842 angstrom. The diselenolate ligands are directed perpendicular to the Cu8 cube faces and are bridged via the Se2C-bite to each of two parallel Cu-Cu edges with an average Cu-Se distance of 2.371 angstrom.