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′)2Cl2] (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)2MoS4 in aqueous MeOH afforded red-violet mixed ligand complexes of the type [(RaaiR′)2Ru(μ-S)2Mo(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 MoVI in MoS42− to MoIV 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).