Structure and spectroscopic studies of cis-bis(bipyridine) cobalt(III) complexes of phenylcyanamide ligands

Several new cobalt complexes, cis-[(bpy)2Co(L)2]PF6, where bpy=2,2′-bipyridine and L=monoanion of phenylcyanamide (pcyd), 2-chlorophenylcyanamide(2-Clpcyd), 2,5-dichlorophenylcyanamide(2,5-Cl2pcyd), 2-methylphenylcyanamide(2-Mepcyd) and 2,4-dimethylphenylcyanamide(2,4-Me2pcyd) have been prepared and characterized by UV–Vis, IR and 1H NMR spectroscopies. The complex of cis-[(bpy)2Co(2-Clpcyd)2]PF6 crystallized with one third of a molecule of acetonitrile with empirical formula of C34.67H25N8.33F6Cl2PCo, in a triclinic crystal system and space group of P with a=10.937(1) Å, b=12.716(1) Å, c=13.452(1) Å, β=91.019(4)°, V=1789.3(3) Å3, and Z=2. The structure was refined by using 5385 Mo Kα reflections with I>3σ(I) and R factor of 0.065. These Co-complexes possess low-energy ligand to metal charge-transfer bands associate with Co(III)NCN chromophore. Comparison between the properties of cis-[Ru(bpy)2(L)2]PF6 and cis-[Co(bpy)2 (L)2]PF6 complexes shows the same behavior in the covalency of the MNCN π-bond.