STRUCTURAL AND SOLID-STATE P-31 NUCLEAR-MAGNETIC-RESONANCE STUDIES ON 1/1/1 MIXED NITROGEN AND PHOSPHINE BASE COMPLEXES WITH COPPER(I) HALIDES

1:1:1 Adducts of copper(i) halides with phosphine and amine donor ligands. [{CuX[PPh(2)(C6H4- Me-o)](cpy)}(2)] and [{CuX(PPh(3))(pip)}(2)] (cpy = 4-cyanopyridine, pip = piperidine; X = Cl, Br or I) have been synthesized as crystalline dihalide-bridged binuclear complexes and characterized by single-crystal structure determinations and solid-state P-31 cross-polarization magic angle spinning (CPMAS) NMR spectroscopy. The [{CuX[PPh(2)(C(6)H(4)Me-o)] (cpy)}(2)] complexes are isomorphous with their PPh(3) analogues, crystallizing as centrosymmetric dimers in space group P2(1)/n with a approximate to 15.5, b approximate to 8.0, c approximate to 18.7 Angstrom, beta approximate to 104 degrees (Z = 2 dimers). Introduction of the o-tolyl group into the phosphine ligand increases all of the Cu-P, Cu-N and Cu-X bond distances by 1-2% with the increase in Cu-X accommodated primarily by an increase in the Cu...Cu distances by 2-6%. For [{CuX(PPh(3))(pip)}(2)] the chloride and bromide complexes are isomorphous, crystallizing in space group Pbca with a approximate to 16.5, b approximate to 18.0, c approximate to 14.6 Angstrom (Z = 4 dimers). The monomer/asymmetric units are disposed close to a centre of symmetry but the two Cu-X distances at each copper site differ by over 0.3 Angstrom and the resultant 'dimers' are better described as associated monomers with three- rather than four-co-ordinate copper. The iodide complex crystallizes in space group P (1) over bar, with a = 17.442(9), b = 16.532(6), c = 13.801(3) Angstrom, alpha = 92.78(2), beta = 112.08(3), gamma = 112.65(3)degrees (Z = 3 dimers). The unit cell contains independent centro- and non-centro-symmetric dimers with significant differences in the geometric parameters of the two. Differences in the Cu-X distances are much smaller than for the X = Cl and Br complexes. The piperidine ligand co-ordinates through the nitrogen lone pair with the Cu-N bond approximately perpendicular to the Cu(2)X(2) plane and is disposed away from the Cu(2)X(2) plane and towards the phosphine ligand for all dimers except the centrosymmetric iodide dimer. The Cu...Cu distances are 7-11% longer than those of the corresponding pyridine base complexes, but are shorter than those in complexes with acetonitrile as the base. The solid-state P-31 CP MAS NMR spectra of the complexes at B = 9.4 T show well resolved asymmetric quartets arising from a combination of scalar and dipolar coupling between the quadrupolar spin3/2 copper and the spin1/2 phosphorus nuclei. The structural and spectroscopic data are discussed in relation to steric and electronic properties of the donor ligands and the influence of these on the size and shape of the CU(2)X(2) core.