Hemilabile phosphonato-phosphane-rhodium catalysts for homogeneous and heterogeneous carbonylation
- Institute for Applied Chemistry, Berlin (Germany)
Phosphonate-phosphanes form with rhodium both chelate and open-chain complexes, which can easily be converted into each other. This property has been used in the development of new and efficient carbonylation catalysts. During the catalytic cycle, the phosphane group is assumed to be coordinated to the transition metal, while the oxygen-donating phosphonate group is supposed to change between a free and a coordinated state, thus vacating or occupying free coordination sites. Activation enthalpies, obtained for hemilabile rhodium catalysts in homogeneous methanol carbonylation, increased significantly with growing distance between phosphonate and phosphane group. While attempts of preparing stable rhodium complex catalysts fixed on silica or alumina for slurry-phase or vapor-phase carbonylations failed, active carbon was found widely superior with respect to the leaching problem. Here, normal diffusion of reactants begins to limit the methanol carbonylation rate. IR-studies confirm the prospect of hemilabile behavior of supported Rh-complexes under reaction conditions.
- OSTI ID:
- 126444
- Report Number(s):
- CONF-950402--
- Country of Publication:
- United States
- Language:
- English
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