Pentamethylcyclopentadienyl-rhodium and -iridium complexes. Part 16. Homogeneous hydrogenation catalysts
- 1 January 1978
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 6,p. 617-626
- https://doi.org/10.1039/dt9780000617
Abstract
A number of pentamethylcyclopentadienyl-rhodium and -iridium complexes catalyse the hydrogenation of olefins under ambient conditions. The complexes [{M(C5Me5)X2}2](X = Cl, Br, or I, and M = Rh or Ir; M = Rh and X = NO3), [{M(C5Me5)}2HX3](M = Rh and X = Cl or Br; M = Ir and X = Cl, Br, or 1) and [{Ir(C5Me5)HX}2](X = Cl or Br) are, in the presence of triethylamine, particularly efficient catalysts in propan-2-ol and, to a lesser extent, in dichloromethane. In the presence of base the µ-chloro-complexes [{M(C5Me5)Cl2}2](M = Rh or Ir) are more active than the µ–hydrido-complexes [{M(C5Me5)}2HxC14–x](M = Rh, x= 1; M = Ir, x= 1 or 2) and the tri-µ- hydrido-complex [{ Ir(C5Me5)}2H3]+ Cl– is inactive. Dienes, acetylenes, and olefins bearing functional groups are readily reduced by [{M(C5Me5)}2HCl3](M = Rh or Ir) at 100 atm and 20 °C; the functional groups were not reduced. The results of preliminary kinetic studies on these systems suggest that alkene hydrogenations in the presence of [{M(C5Me5)Cl2}2](M = Rh or Ir) and [{Ir(C5Me5)HCl}2] involve monomeric active species whereas those carried out using [{M(C5Me5)}2HC13](M = Rh or Ir) proceed via dimeric intermediates.Keywords
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