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 α-N heterocyclic ketone

Abstract

A series of ruthenium(II) complexes of the NNS donor ligand methyl 2-pyridyl ketone 4-(4-tolyl)thiosemicarbazone (HL) has been synthesized using RuCl₃·xH₂O and [Ru(PPh₃)₃Cl₂]: [Ru(HL)₂][ClO₄]₂ 1, [Ru(L)(PPh₃)₂Cl] 2, [Ru(HL)(PPh₃)₂Cl]Cl 3, [Ru(HL)(PPh₃)₂Cl]PF₆ 4, [Ru(L)(PPh₃)(bpy)]PF₆ 5, [Ru(L)(PPh₃)(dppe)]PF₆ 6, [Ru(HL)(PPh₃)(pic)]PF₆ 7 and [Ru(HL)(PPh₃)(mpi)]Cl₂ 8 [where bpy = 2,2′-bipyridine, dppe = 1,2-bis(diphenylphosphino)ethane, Hpic = pyridine-2-carboxylic acid, mpi = methyl(2-pyridyl)methyleneimine]. Chemical and electrochemical studies have been carried out. Structures of the compounds 3·CH₂Cl₂ 3 and 8·CH₂Cl₂·3H₂O have been determined by single crystal X-ray diffraction. The thione form of the ligand (HL) is chelated to the ruthenium centre through the pyridine nitrogen, imine nitrogen and the thione sulfur atom. The existence of a new unstable ligand methyl(2-pyridyl)methyleneimine (mpi) co-ordinated to Ru^II through the pyridine and imine nitrogen atoms was confirmed from the crystal structure of compound 8.