Synthetic, spectroscopic, and X-ray crystallographic studies on phenylcyanamidocopper(II) complexes. The characterization of three different co-ordination modes for phenylcyanamide anions

Abstract

Phenylcyanamidocopper(II) complexes of the type [{CuL(L′)₂}₂][L = 2,2′-bipyridine (bipy) or 1,10-phenanthroline (phen), L′= a phenylcyanamide ion, XC₆H₄NCN^–], [CuL₂(L′)₂](L = pyridine or piperidine), and [{CuL(L′)(CH₃CO₂)}₂](L = bipy or phen) have been prepared from the reaction of the neutral phenylcyanamides with copper(II) acetate monohydrate in the presence of the appropriate N-donor co-ligand. They have been characterized by magnetic, i.r., and electronic spectral techniques and the crystal and molecular structures of [{Cu(bipy)(PhNCN)₂}₂] and [{Cu(phen)(3-ClC₆H₄NCN)(CH₃CO₂)}₂]·2H₂O determined by single-crystal X-ray diffraction techniques. Crystals of [{Cu(bipy)(PhNCN)₂}₂] are monoclinic, space group P2₁/c, with a= 9.625(3), b= 20.945(5), c= 9.956(3)Å, β= 97.10(2)°, and Z= 2. The complex consists of discrete centrosymmetric dimers. The copper atom of each monomeric unit is co-ordinated equatorially to two bipy nitrogens [Cu–N 2.012(5) and 2.052(5)Å] and to the cyano-nitrogens of two phenylcyanamide ligands [Cu–N 1.938(5) and 1.942(6)Å]. The distorted square-pyramidal geometry is completed by a longer axial bond [2.355(6)Å] to the amido nitrogen of one of the phenylcyanamide ligands of the other half of the dimer. Crystals of [{Cu(phen)(3-ClC₆H₄NCN)(CH₃CO₂)}₂]·2H₂O are triclinic, space group P, with a= 8.171 (5), b= 10.060(6), c= 13.377(7)Å, α= 74.33(4), β= 84.79(5), γ= 72.24(4)°, and Z= 1. The complex consists of discrete centrosymmetric dimers, dimerization being achieved by the cyano nitrogen of the 3-chloro-phenylcyanamide ligand asymmetrically bridging two copper atoms, which have an approximate square-pyramidal co-ordination geometry. The cyano nitrogen [Cu–N 1.950(6)Å], two phen nitrogens, and an acetate oxygen make an ‘ON₃’ basal plane. A longer apical bond to the cyano nitrogen of the cyanamide ligand of the other half of the dimer [Cu–N 2.454(6)Å] completes the co-ordination. The identification of three different co-ordination modes for the anionic phenyl-cyanamide ligands establishes their ambidentate nature.