DEPENDENCE OF THE RU(III)-CYANAMIDE CHROMOPHORE ON INNER-SPHERE COORDINATION - COMPARISON OF CIS-[RU(BPY)(2)(PCYD)(2)](+) AND [RU(NH3)(5)(PCYD)](2+) COMPLEXES

Six bis(bipyridine)ruthenium(II) complexes of chloro-substituted pheny lcyanamide anion ligands cis-[Ru(bpy)(2)-(L)(2)], where L = monoanions of phenylcyanamide (pcyd), (2-chlorophenyl)cyanamide (2-Cl-pcyd), (2, 3-dichlorophenyl)cyanamide (2,3-Cl(2)pcyd) (2,4,5-trichloro-phenyl)cya namide (2,4,5-Cl(3)pcyd), (2,3,4,5-tetrachlorophenyl)cyanamide (2,3,4, 5-Cl(4)pcyd) and (pentachlorophenyl)cyanamide (Cl(5)pcyd), have been s ynthesized and characterized by elemental analysis,H-1-NMR, IR, and UV -vis near-IR spectroscopies, and cyclic voltammetry. Oxidation of the complexes by controlled-potential electrolysis generated cis-[Ru(bpy)( 2)(L)(2)](+). These Ru(III) complexes possess low-energy ligand to met al charge-transfer bands that are associated with the Ru(III)-NCN chro mophore. A spectroscopic analysis of these LMCT transitions, which ass umed C-2v microsymmetry about Ru(III), determined their electronic ori gins. Differences between the properties of [Ru(NH3)(5)L](2+) and [Ru( bpy)(2)(L)(2)](+) complexes suggest that for the latter the covalency of the Ru(III)-NCN pi bond has significantly increased.