title: Synthesis, structure, and electrochemical properties of a family of 2-(arylazo)phenolate complexes of ruthenium with unusual C-C coupling and N=N cleavage.
abstract: Reaction of 2-(4'-R-phenylazo)-4-methylphenols (R = OCH3, CH3, H, Cl, and NO2) with [Ru(dmso)(4)Cl2]affords a family of five ruthenium(III) complexes, containing a 2-(arylazo)phenolate ligand forming a six-membered chelate ring and a tetradentate ligand formed from two 2-(arylazo)phenols via an unusual C-C coupling linking the two ortho carbons of the phenyl rings in the arylazo fragment. A similar reaction with 2-(2'-methylphenylazo)-4-methylphenol with [Ru(dmso)(4)Cl2] has afforded a similar complex, in which one 2-(2'-methylphenylazo)-4-methylphenolate ligand is coordinated forming a six-membered chelate ring, and the other two ligands have undergone the C-C coupling reaction, and the coupled species is coordinated as a tetradentate ligand forming a five-membered N,O-chelate ring, a nine-membered N,N-chelate ring, and another five-membered chelate ring. Reaction of 2-(2',6'-dimethylphenylazo)-4-methylphenol with [Ru(dmso)(4)Cl2] has afforded a complex in which two 2-(2',6'-dimethylphenylazo)-4-methylphenols are coordinated as bidentate N,O-donors forming five- and six-membered chelate rings, while the third one has undergone cleavage across the N=N bond, and the phenolate fragment, thus generated, remains coordinated to the metal center in the iminosemiquinonate form. Structures of four selected complexes have been determined by X-ray crystallography. The first six complexes are one-electron paramagnetic and show rhombic ESR spectra. The last complex is diamagnetic and shows characteristic 1H NMR signals. All the complexes show intense charge-transfer transitions in the visible region and a Ru(III)-Ru(IV) oxidation on the positive side of SCE and a Ru(III)-Ru(II) reduction on the negative side.
authors.affiliation: Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, Kolkata 700 032, India.
authors.forename: Sarmistha
authors.initials: S
authors.lastname: Halder
authors.forename: Rama
authors.initials: R
authors.lastname: Acharyya
authors.forename: Shie-Ming
authors.initials: SM
authors.lastname: Peng
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Michael G B
authors.initials: MG
authors.lastname: Drew
authors.forename: Samaresh
authors.initials: S
authors.lastname: Bhattacharya
mesh_terms: D002244:Carbon / Q000737:chemistry; D015392:Chemistry, Inorganic / Q000379:methods; D018360:Crystallography, X-Ray; D004563:Electrochemistry / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry; D010636:Phenols / Q000737:chemistry; D017975:Ruthenium Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D010636:Phenols; D017975:Ruthenium Compounds; D002244:Carbon; D009584:Nitrogen