Synthetic, spectroscopic and X-ray crystallographic studies on phenylcyanamidocopper(I) complexes

Abstract

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)Å 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)Å], two phosphorus atoms from a chelating dppe and one from the bridging dppe making up the co-ordination sphere. Crystals of [{Cu(PPh₃)₂(4-MeC₆H₄NCN)}₂] are monoclinic, space group P2₁/n, with a= 15.003(2), b= 13.844(2), c= 18.711(2)Å, β= 101.22(1)° and Z= 2. This complex is a centrosymmetric dimer with the [4-MeC₆H₄NCN]^– ligands bridging in a µ-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)Å] and an amido nitrogen from the centrosymmetrically related [4-MeC₆H₄NCN]^– ligand [Cu–N 2.095(2)Å]. 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)³¹P 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.