Synthesis of Manganese Oxide Clusters with Oxidation Catalysis

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We synthesized Mn-Mo and Rh-W oxide clusters with tacn (1,4,7-triazacyclononane) derivatives and Cp (cyclopentadienyl) ligands, respectively. Their ability of oxidation catalysis for hydrocarbon compounds was examined.A reaction of the dinuclear oxometalate of [(n-Bu_4)N]_2[Mo_2O_7] and (tacn) MnCl_3 in water afforded a new cubic type of the Mn-Mo mixed metal oxide cluster of [{(tacn)Mn}_2Mo_4O_<16>]-4H_2O (1). An X-ray analysis of 1 reveals that it is composed of a cubic framework consisting of one Mn(IV), three Mo (VI) ions and four oxygen atoms. It also has an incomplete cubic framework formed by three Mo (VI) ions and four oxygen atoms.We examined catalytic ability of 1 towards the bleaching of pinacyanol chloride dye (PC dye). In the reaction using 1 the blue color of the dye disappeared in 6h in water under heterogeneous conditions : hydrogen peroxide (15 mol), PC dye (15 mol) and catalyst (1.5 mol). This preliminaly results show that cluster 1 is able to use a mild bleaching catalyst for a heterogeneous system.Rh-W oxide clusters with the Cp^* ligand were prepared in two geometrical isomers of [(Cp^*Rh)_4W_4O_<16>] from the reaction of the mononuclear [WO_4]^<2-> with [Cp^*RhCl(μ-Cl)]_2 in CH_3CN : two geometrical isomers have a windmill and a triple cubane geometrical framework. The former was formed selectively below 20℃. Above 60℃ the latter was obtained specifically in the same reaction system. We studied the mechanisms for the isomerization and the formation of those isomers by using ^<17>O NMR spectroscopy and ESI-MS.It is found that a species with a ladder structure plays an important role for both the isomerization and the formation of the isomers.