STUDY OF THE GEOMETRIC PREFERENCES OF COPPER(I) HALIDE COORDINATION-COMPOUNDS WITH TRIARYLPHOSPHINES - CRYSTAL-STRUCTURES OF [CUCL(P(O-TOLYL)3)]2 AND [CUBR(P(O-TOLYL)3)]2

The crystal structures of [CuCl(totP)]2 and [CuBr(totp)]2, totP = tri-o-tolylphosphine, are reported. They present planar Cu2X2 cores with trigonal-planar Cu(I) atoms, the Cu-P axes bisecting in both cases the X-Cu-X angles. Crystallographic data: for [CUCl(totP)]2 a=9.1758(7), b=10.4805(8), c=20.481(1) angstrom, beta=99.279(2)-degrees, with Z=2 and space group P2(1)/n; for [CuBr(totP)]2 a=9.215(1), b=10.203(1), c=11.275(1) angstrom, alpha=78.422(5), beta=100.691(5), gamma=80.789(4)-degrees, with Z = 1 and space group P1BAR. The slight geometric changes observed between the two compounds, especially the more acute X-Cu-X angle in the case Of [CuCl(totP)12 are investigated with Extended Huckel calculations on model compounds.