title: Binuclear ruthenium(III) bis(thiosemicarbazone) complexes: synthesis, spectral, electrochemical studies and catalytic oxidation of alcohol.
abstract: A new series of binuclear ruthenium(III) thiosemicarbazone complexes of general formula [(EPh3)2(X)2Ru-L-Ru(X)2(EPh3)2] (where E=P or As; X=Cl or Br; L=NS chelating bis(thiosemicarbazone ligands) has been synthesized and characterized by analytical and spectral (FT-IR, UV-Vis and EPR). IR spectra show that the thiosemicarbazones behave as monoanionic bidentate ligands coordinating through the azomethine nitrogen and thiolate sulphur. The electronic spectra of the complexes indicate that the presence of d-d and intense LMCT transitions in the visible region. The complexes are paramagnetic (low spin d(5)) in nature and all the complexes show rhombic distortion around the ruthenium ion with three different 'g' values (gx≠gy≠gz) at 77K. All the complexes are redox active and exhibit an irreversible metal centered redox processes (Ru(III)-Ru(III)/Ru(IV)-Ru(IV); Ru(III)-Ru(III)/Ru(II)-Ru(II)) within the potential range of 0.38-0.86V and -0.39 to -0.66 V respectively, versus Ag/AgCl. Further, the catalytic efficiency of one of the complexes [Ru2Cl2(AsPh3)4(L1)] (4) has been investigated in the case of oxidation of primary and secondary alcohols into their corresponding aldehydes and ketones in the presence of N-methylmorpholine-N-oxide(NMO) as co-oxidant. The formation of high valent Ru(V)O species is proposed as catalytic intermediate for the catalytic cycle.
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India.
authors.forename: M
authors.initials: M
authors.lastname: Mohamed Subarkhan
authors.affiliation: School of Chemistry, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India. Electronic address: ramesh_bdu@yahoo.com.
authors.forename: R
authors.initials: R
authors.lastname: Ramesh
mesh_terms: D000438:Alcohols / Q000737:chemistry*; D002384:Catalysis; D003497:Cyclic N-Oxides / Q000737:chemistry; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D004581:Electronics; D006219:Halogens / Q000737:chemistry; D008024:Ligands; D008280:Magnetics; D015394:Molecular Structure; D009025:Morpholines / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared; D013455:Sulfur / Q000737:chemistry; D013882:Thiosemicarbazones / Q000737:chemistry*
chemical_list: D000438:Alcohols; D003497:Cyclic N-Oxides; D006219:Halogens; D008024:Ligands; D009025:Morpholines; D010087:Oxides; D013882:Thiosemicarbazones; D013455:Sulfur; D012428:Ruthenium; C067960:4-methylmorpholine N-oxide; D009584:Nitrogen; D010100:Oxygen
keywords: Binucleating thiosemicarbazone ligands; Oxidation of alcohol; Redox property; Ruthenium(III) complexes; Spectra; Synthesis