Interest in supported metal cluster catalysts is increasing as evidence of industrial catalysts with less than about 10 metal atoms per cluster is emerging. We report the synthesis [from Rh(C2H4)2(acac)] and characterization of well-defined supported mononuclear rhodium complexes Rh(C2H4)2 and small rhodium clusters (including dimers). IR and X-ray absorption spectra representing the supported species during cluster formation and catalysis give evidence of Rh�ligand, Rh�support, and Rh�Rh bonds. Cluster formation is controlled by the support and reactive atmosphere providing ligands. The electron-donating support MgO slows H2-induced cluster formation from Rh(C2H4)2 by hindering hydrogenation of ethene ligands, but the electron-withdrawing support zeolite HY increases the stability of the rhodium complexes when CO is a ligand. The catalytic activity and selectivity for reactions of ethylene and 1,3-butadiene in the presence of H2 are markedly influenced by the nuclearity of the rhodium species and the ligands.

Tailored supported rhodium cluster catalysts

245th National Meeting (2013)

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