Infrared spectra and catalytic activity of supported molybdenum hexacarbonyl

Infrared spectroscopy has been used to study the olefin disproportionation catalysts consisting of molybdenum hexacarbonyl supported on silica, alumina and magnesia. Activation of the catalysts is found to cause decomposition of the molybdenum hexacarbonyl. Decomposition occurs most readily on a silica support which is not able to stabilize intermediate sub-carbonyl species. The intermediate sub-carbonyl species observed on alumina and magnesia supports are not active centres for olefin disproportionation; the active species is formed by complete loss of all six carbonyl ligands. Indirect evidence suggests the active species is not molybdenum(0) but some higher oxidation state.