| Research Abstract |
Application of halide clusters of Nb, Ta ([(M_6Cl1_2)Cl_2(H_2O)_4]・4H_2O(M=Nb,Ta)),Mo,W(((H_3O)_2[(M_6Cl_8)Cl_6]・6H_2O(M =Mo,W)), and Re([Re_3Cl_9]) as catalysts was made in a gas flow reactor under a hydrogen or helium stream. When the halide cluster was treated above 150℃, evolution of hydrogen chloride was deteced. Above this temperature, decomposition of phenyl acetate to phenol and ketene, dehydration of alcohol to olefin or ether, isomerization of olefinic double bond, and dehydrohalogenation of halogenated alkane proceeded over halide cluster catalyst. Thus, a novel research area of halide cluster catalysis was initiated after 143 years of the first report for the synthesis of molybdenum chloride. These reactions are catalyzed by conventional solid acid catalysts. Analyses of adsorbed pyridine over the activated cluster catalyst showed the presence of Brensted acid site, which would be attributable to the hydroxo ligand such as [(Mo_6Cl_8)Cl_4(OH_2)(OH)].
Dehydrogenation and dealkylation, which are catalyzed by platinum group metals, and polymerization, which is catalyzed by group 4 transition metal compounds, are revealed to be catalyzed by halide cluster. We are planning to study the scope and limitations of halide cluster catalysis and to develop unique reaction that is catalyzed by halide cluster. The goal of this study is to construct a new research area of "halide cluster catalysis."
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