ANION DESIGN BY CHOICE OF CATION - ISOLATION OF A DINUCLEAR CHLOROCUPRATE(I) ANION CONTAINING TRIGONALLY COORDINATED COPPER(I) USING THE TETRAETHYLPHOSPHONIUM CATION

A centrosymmetric di-mu-chloro-dichlorodicuprate(I) ion, [Cu2Cl4]2-, has been prepared by selecting the tetraethylphosphonium cation as counter-ion, on the basis of its size in comparison with those of related symmetrically substituted phosphonium and ammonium cations. The copper(I) centres in [Cu2Cl4]2- exhibit distorted trigonal coordination and the anion can be seen as a loose association of [CuCl2]- moieties, in which the Cu-Cl bonds are 2.112(3) and 2.136(3) angstrom, joined by two long Cu ... Cl interactions of 2.922(3) angstrom. The Cu ... Cu and Cl ... Cl separations are 3.515(2) and 3.722(5) angstrom, respectively. [P(C2H5)4]2[Cu2Cl4] crystallizes in space group P2(1)/n with a = 11.881(4), b = 7.976(3), c = 14.296(2) angstrom, beta = 112.46(2)-degrees, at - 150-degrees-C, and Z = 2. Full-matrix least-squares refinement yielded a final R = 0.051 (R(w) = 0.066) for 109 parameters and 1266 observed reflections.