A novel series of sulphur-bridged ruthenium-molybdenum complexes:: [(RaaiR')2 Ru(μ-S)2Mo(OH)2].: Synthesis, spectroscopic and electrochemical characterization.: RaaiR'=1-alkyl-2-(arylazo) imidazole

The reaction of ctc-[Ru(RaaiR')(2)Cl-2] (1) [RaaiR' = 1-alkyl-2-(arylazo) imidazole, p-R-C6H4-N=N-C3H2NN(1)-R', R = H (a), Me (b), Cl (c), R' = Me (2), Et (3), Bz (4) ] with (NH4)(2)MoS4 in aqueous MeOH afforded red-violet mixed ligand complexes of the type [(RaaiR')(2)Ru(mu-S)(2)Mo(OH)(2)] (2-4). In complexes (2-4) the terminal Mo=S bonds of the MoS42- unit become hydroxylated and the molybdenum ion is reduced from the starting Mo-VI in MoS42- to Mo-IV in the final product (2-4). The solution electronic spectra exhibit a strong MLCT band at 550-570 nm in DCM. Cyclic voltammograms show a Ru(III)/Ru(II) couple at 1.10-1.4 V, irreversible Mo(IV)/Mo(V) oxidations in the 1.66-1.72 V range, along with four successive reversible ligand reductions in the range -0.45-0.67 V (one electron), 0.82-1.12 V (one electron), and -1.44-1.90 V (simultaneously two electrons).