SYNTHETIC, SPECTROSCOPIC AND X-RAY CRYSTALLOGRAPHIC STUDIES ON PHENYLCYANAMIDOCOPPER(I) COMPLEXES

The preparations of phenylcyanamidocopper(I) complexes of the types [Cu2(dppe)3L2].2Me2CO [dppe = 1,2-bis(diphenylphosphino)ethane, L = a phenylcyanamide ion] and [{Cu(PPh3)2L}2] are described. The crystal structures of two of the complexes, namely [Cu2(dppe)3(4-ClC6H4NCN)2].2Me2CO (4-ClC6H4NCN = 4-chlorophenylcyanamide) and [{Cu(PPh3)2 (4-MeC6H4NCN)}2] (4-MeC6H4NCN = 4-methylphenylcyanamide) have been determined by X-ray diffraction techniques. Crystals of [Cu2(dppe)3(4-ClC6H4NCN)2].2Me2CO are orthorhombic, space group Pbca, with a = 22.397(14), b = 18.970(7), c = 20.341(5) angstrom and Z = 4. The complex contains centrosymmetric dppe-bridged dinuclear molecules. Each copper atom has a distorted tetrahedral geometry with the cyano nitrogen from a terminally bound [4-ClC6H4NCN]- ligand [Cu-N 1.967(5) angstrom], two phosphorus atoms from a chelating dppe and one from the bridging dppe making up the coordination sphere. Crystals of [{Cu(PPh3)2(4-MeC6H4NCN)}2] are monoclinic, space group P2(1)/n, with a = 15.003(2), b = 13.844(2), c = 18.711(2) angstrom, beta = 101.22(1)-degrees and Z = 2. This complex is a centrosymmetric dimer with the [4-MeC6H4NCN]- ligands bridging in a mu-1,3 fashion. Each copper atom has a distorted tetrahedral geometry, being bound to two PPh3 phosphorus atoms, a terminal cyano nitrogen atom from a [4-MeC6H4NCN]- ligand [Cu-N 2.045(2) angstrom]. The v(CN) stretching vibration for the co-ordinated phenylcyanamides occurs in the 2125-2175 cm-1 range. Solid-state cross-polarisation magic-angle-spinning (CP-MAS) P-31 NMR spectra at 121.47 MHz for the complexes [{Cu(PPh3)2L}2] (L = XC6H4NCN; X = 4-Me, 4-Cl or H) consist of two well resolved quartets of doublets arising from each of the crystallographically independent phosphorus nuclei. The doublet structure is a consequence of homonuclear phosphorus-phosphorus two-bond coupling [2J(P1-P2) = 120 Hz]. Available structural data for phenylcyanamidocopper complexes are summarised and comparison made with related pseudohalide complexes.