Synthesis and electrochemical properties of p-cymene-ruthenium(II) complexes with (EPPh2)(2)CHR (E=S, Se; R=H, Me) and their anionic derivatives as ligands. Crystal structure of [(eta(6)-MeC6H4Pri)Ru{eta(3)-(SPPh2)(2)CMe-C,S,S'}]PF6

The synthesis and properties of cationic complexes of general formula [(eta(6)-MeC6H4Pri)RuCl{eta(2)-(EPPh2)(2)CHR-E,E'})]BF4 (R = H, E = S (1), Se (2); R = Me, E = S (5)) are described. The methylene proton of the coordinated dichalcogenide ligand reacts with strong bases such as KOH in methanol or TIPz in dichloromethane solutions, to give new cationic complexes in which the anionic ligand is acting as tridentate chelate with a C,E,E'-donor set, [(eta(6)-MeC6H4Pri)Ru{eta(3)-(EPPh2)(2)CR-C,E,E'})]A (R = H, A = BF4-, E = S (3), Se (4); R = Me, A = PF6-, E = S (6)). The complexes have been characterised by elemental analyses, molar conductivities and IR and NMR spectroscopy. The structure of the title complex was established by X-ray crystallography. The crystals are tetragonal; at 293 degrees C a = 15.120(2), c = 16.090(3) Angstrom, space group P4(3), Z = 4. The complex contains a tridentate C,S,S'-bonded ligand occupying three coordination positions of a distorted octahedral ruthenium centre, with an eta(6)-MeC6H4Pri group completing the coordination sphere. Cyclic voltammetry shows that under argon the acidic protons of the coordinated neutral disulfide ligands (1, 5) are reduced to hydrogen yielding the complexes with the anionic ligand coordinated in their tridentate form (3, 6). These compounds are irreversibly reduced in a one-electron process to give Ru(I) species, followed by chemical decomposition.