Sulphur-bridged ruthenium – molybdenum complexes: [(R-aapm)2Ru(μ-S)2Mo(OH)2]. Synthesis, spectroscopic and electro-chemical characterization. R-AAPM = 2-(arylazo)pyrimidine

Abstract

The reaction of ctc-[Ru(R-aapm)2Cl2] (1) with (NH4)2MoS2 in aqueous MeOH afforded redviolet mixed ligand complexes of the type [(R-aapm)2Ru(μ-S)2Mo(OH)2] (2a-2e) [R-aapm = 2-(arylazo) pyrimidine,p-R-C6H4-N=N-C4H3NN, R = H (2a), Me (2b), Cl (2c), OMe (2d), NO2 (2e)]. In complexes (2a-2e) the terminal Mo=S bonds of the MoS unit get hydroxylated and the molybdenum ion is reduced from the starting MoVI in MoS to MoIV in the final product. The solution electronic spectra ex-hibit a strong MLCT band at 550–570 nm in DCM. The1H NMR spectra confirms the geometry of the complexes as being that ofcistranscis isomers. 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),-1.44–1.90 V (simultaneously two electrons).