COPPER(I) AND GOLD(I) COMPLEXES WITH CIS-BIS(DIPHENYL-PHOSPHINO)ETHYLENE - CRYSTAL-STRUCTURES AND P-31 CROSS-POLARIZATION MAGIC ANGLE SPINNING NUCLEAR-MAGNETIC-RESONANCE STUDIES

The synthesis, structural and solid-state P-31 cross-polarization magic angle spinning (CP MAS) NMR characterization of cis-bis(diphenylphosphino)ethylene (dppey) and the copper(I) and gold(I) complexes [M(dppey)2]PF6 has been carried out. The complexes, which have been shown to exhibit cytotoxic and antitumour activity, belong to the relatively rare class of copper(I) and gold(i) complexes with tetrahedral CuP4 and AuP4 co-ordination spheres. Crystals of dppey 1 are monoclinic with space group P2(1)/c and a = 12.861(8), b = 13.097(2), c = 14.228(8) angstrom, beta = 116.15(3)-degrees; R was 0.047 for 3117 'observed' reflections. The solid-state CP MAS P-31 NMR spectrum consists of an AB multiplet with delta(P(A)) -24.2, delta(P(B)) -27.2 and J(P-P) = 126 Hz. Crystals of [Cu(dppey)2]PF6 2 are orthorhombic with space group P2(1)2(1)2(1) and a = 14.479(5), b = 16.703(4), c = 20.891(4) angstrom; R was 0.046 for 3138 'observed' reflections. The CuP4 co-ordination sphere is regular within the constraints of chelation with Cu-P in the range 2.276(2)-2.289(2) angstrom. The copper atom lies on a pseudo two-fold axis of symmetry bisecting the C=C bonds. Charge-transfer interactions between phenyl rings on each ligand contribute to the stabilization of the structure of the cation. The solid-state P-31 NMR spectrum consists of four broad bands (DELTAnu1/2 = 300 Hz) centred at delta 8 with J(Cu-P) almost-equal-to 820 Hz. Distortion of the quartet spacings by quadrupolar interaction with the copper nuclei is minimal. Crystals of [Au(dppey)2]PF6 3 are isomorphous with 2 with a = 14.644(4), b = 16.703(1), c = 20.699(5) angstrom; R was 0.025 for 3947 'observed' reflections. The Au-P distances lie in the narrow range 2.377(2)-2.388(2) angstrom. Solid-state CP MAS P-31 NMR of this complex and the analogous nitrate and chloride complexes at magnetic field strengths of 2.11, 7.05 and 9.40 T reveal splitting of the phosphorus signal into a quartet ascribed to Au-P spin-spin coupling effects with J(Au-P) estimated to be 200 Hz. As for the copper complex, distortion of the quartet spacings is minimal and indicative of a small Au-197 quadrupolar coupling constant. Solution and solid-state P-31 NMR chemical shift parameters are similar, supporting the hypothesis that the tetrahedral bis(chelated) cations are also stable in solution. Spin-spin coupling to the quadrupolar (Au-197 or Cu-63/65) nuclei was not resolved in the solution spectra, however, due to rapid quadrupolar relaxation.