Electrochemical Generation of Complexes Containing Heterometallic Trinuclear Triangular Metal-Sulphur-Cubiodal {M’M2S4}4+ Core (where M and M’ = Mo and W): Synthesis and Study of Physico-chemical Behaviour

Chromatographic separation of mixture leads to the isolation of molybdenum-tungsten mixed-metal clusters [MoW2S4(H2O)9] 4+ and [WMo2S4(H2O)9] 4+ .From the aqua ion the corresponding oxalato-derivatives as [MoW2S4(C2O4)3(H2O)3] 2-and [WMo2S4(C2O4)3(H2O)3] 2- are isolated.The peak positions of the two big bands in each infrared spectrum of the four aqua clusters, [Mo3S4(H2O)9] 4+ , [W3S4(H2O)9] 4+ , [MoW2S4(H2O)9] 4+ and [WMo2S4(H2O)9] 4+ in the 550-400 cm -1 region shift to lower wave number when the molybdenum atom is replaced by tungsten.The cyclic voltammogramms of Cs2[MoW2S4(C2O4)3(H2O)3] (1)B and Cs2[WMo2S4(C2O4)3(H2O)3] (2) shows three consecutive one-electron reduction steps in the aqueous medium with supporting electrolyte, KCl at -0.84, -1.40, -1.78 and -0.73, -1.22, -1.66 V, respectively.These steps correspond to the change of oxidation states of three metals in each cluster with the following electronic configuration {M3} 6 → {M3} 7 → {M3} 8 → {M3} 9 .The half wave potential E1/2 are significantly dependent on the cluster metals.In all the reduction processes the [MonW3-nS4(C2O4)3(H2O)3] 2-clusters (n = 0-3) are easily reduced with the increase in the number of Mo(n) in the clusters.The proceeding reduction centre of themolybdenum-tungsten mixed metal clusters is mainly on the Mo atom(s) rather than W atoms.