Dinuclear copper complexes with cyanamide derivatives as bridging ligands

Three mixed-valence copper complexes [{Cu(phen)(2)}(2)(mu-L)](PF6)(2) (where phen = 1, 10-phenanthroline, L = 1,4-dicyanamidobenzene (dicyd)), 1,4-dicyanamido-2,5-dimethylbenzene (Me(2)dicyd) and 1,4-dicyanamido-2,5-dichlorobenzene (Cl(2)dicyd), and one dinuclear Cu(II) complex [{Cu(phen)(2)}(2)(mu-apc)](PF6)(3) (where ape = monoanion of 4-azo(phenyleyanamido)benzene) have been prepared and characterized by elemental analysis, IR and electronic absorption spectroscopies and cyclic voltammetry. [{Cu(phen)(2)}(2)(mu-apc)](PF6)(3) center dot 2CH(3)COCH(3) crystallized in the triclinic system and both five-coordinate Cu(II) ions in the dinuclear unit are linked through a bridging 4-azo(phenylcyanamido)benzene (apc) ligand. The cyanamide group (NCN) of the bridging ligand is coordinated to Cu(II) ions through the cyano-nitrogen and amido-nitrogen. The bond length between Cu(1) and cyano-nitrogen is slightly larger than that formed by Cu(2) and amido-nitrogen. The angular structural index parameters, tau, for Cu(1) and Cu(2) are 0.9 and 0.5, respectively. The copper(II) atoms display a different geometry with a N-5 chromophore group. The intra Cu...Cu separation is 5.156(1) angstrom. All of the dicyd dinuclear copper complexes show radical anion absorption. (C) 2008 Elsevier Ltd. All rights reserved.