Structural and 31P CP MAS NMR spectroscopic studies of the P2CuN2 copper(I) complexes [Cu(PPh3)2(MeCN)2]X for X = PF6, BF4 and ClO4

The mixed ligand P2CuN2 copper(I) complexes [Cu(PPh3)(2)(MeCN)(2)]X have been studied by one- and two-dimensional P-31 CP MAS NMR spectroscopy for X = PF6, BF4 or ClO4 and single crystal X-ray diffraction for X = PF6 and ClO4, completing availability of precise structural data for this isomorphous series. The compounds crystallise as discrete cations and anions in space group P2(1)/n with a approximate to 15, b approximate to 27, c approximate to 9 Angstrom, beta = 95 degrees, Z = 4. The anion is located ca. 6 Angstrom from the copper atom and adjacent to a cleft formed between the acetonitrile ligands and phosphine ligand 2 while the crystallographically independent PPh3 ligands adopt staggered three-bladed propeller-type conformations of opposite chirality. The geometric symmetry of the P2CuN2 co-ordination sphere is low with Cu-P(1) 2.276(4)-2.287(2), Cu-P(2) 2.258(4)-2.269(1) Angstrom, Cu-N 2.023(9)-2.053(3) Angstrom, P-Cu-P 126.82(4)-127.73(5), N-Cu-N 99.5(4)-100.3(1), P(1)-Cu-N 100.87(8)-102.34(9) and P(2)-Cu-N 110.4(1)-111.9(3)degrees. One- and two-dimensional solid state P-31 CP MAS NMR spectra of the compounds at 9.40 T show chemical shift differences of 6 ppm between the signals arising from the two P sites which form part of an ABX spin system with (1)J[(31)p(1)-(CU)-C-63] 1.13-1.14 kHz, (1)J[(31)p(2)-(CU)-C-63] 1.30 kHz and (2)J(P-31-P-31) 75 Hz. The copper quadrupolar induced distortion of the line spacings is different for the two sites and is postulated to be a consequence of variation in the angle between the Cu-P vectors and the z axis of the electric field gradient tensor. The magnitude of the distortion is relatively small and consistent with small copper quadrupolar coupling constants for the compounds and a balanced electronic charge distribution about the copper(I) site in spite of the low geometric symmetry of the PxCuN2 co-ordination sphere.