Chemistry of ruthenium(II) complexes of the tridentate NNS donor methyl 2-pyridyl ketone 4-(4-tolyl)thiosemicarbazone. Isolation and structural characterisation of a novel ruthenium(II) complex containing a co-ordinated imine of an alpha-N heterocyclic ketone

A series of ruthenium(II) complexes of the NNS donor ligand methyl 2-pyridy l ketone 4-(4-tolyl)thiosemicarbazone (HL) has been synthetized using RuCl3 . xH(2)O and [Ru(PPh3)(3)Cl-2]: [Ru(HL)(2)][ClO4](2) 1, [Ru(L)(PPh3)(2)Cl] 2, [Ru(HL)(PPh3)(2)Cl]Cl 3, [Ru(HL)(PPh3)(2)Cl]PF6 4, [Ru(L)(PPh3)(bpy)]PF6 5, [Ru(L)(PPh3)(dppe)]PF6 6, [Ru(HL)(PPh3)(pic)]PF6 7 and [Ru(HL)(PPh3)(mp i)]Cl-2 8 [where bpy = 2,2'-bipyridine, dppe = 1,2- bis(diphenylphosphino)e thane, Hpic = pyridine-2-carboxylic acid, mpi = methyl(2-pyridyl)methylenei mine]. Chemical and electrochemical studies have been carried out. Structur es of the compounds 3 . Ch(2)Cl(2) 3 and 8 . CH2Cl2. 3H(2)O have been deter mined by single crystal X-ray diffraction. The thione form of the ligand (H L) is chelated to the ruthenium centre through the pyridine nitrogen, imine nitrogen and the thione sulfur atom. The existence of a new unstable ligan d methyl(2-pyridyl)methyleneimine (mpi) co-ordinated to Ru-II through the p yridine and imine nitrogen atoms was confirmed from the crystal structure o f compound 8.