Synthesis, structure and spectroscopic study of RhIII polypyridine complexes with phenylcyanamide derivative ligands

Several new RhIII complexes, [Rh(tpy)(bpy)L](PF6)2 (tpy=2,2′:6′,2″-terpyridine, bpy=2,2′-bipyridine, and L=monoanions of phenylcyanamide(pcyd)), 4-methylphenylcyanamide (4-MePcyd), 2,4-dimethylphenylcyanamide (2,4-Me2pcyd), 4-methoxyphenylcyanamide (4-MeOPcyd), 2-chlorophenylcyanamide (2-Clpcyd) and 2,5-dichlorophenylcyanamide (2,5-Cl2pcyd) have been synthesized and characterized by elemental analysis, IR, 1H NMR and electronic absorption spectroscopies. ORTEP drawing of [Rh(tpy)(bpy)(2,5-Cl2pcyd)](PF6)2·1/2CH3CN shows three pyridyl rings of the tpy ligand that are nearly coplanar, as are the two rings of bpy. The anionic cyanamide group is coordinated end-on by the nitrile nitrogen to the RhIII. The RhIII-NCN bond is bent, having an angle of 125.4°. This bent bond is largely determined by the σ-bonding interaction of a cyanamide non-bonding electron pair in a sp2 hybrid orbital.