Addition of H-2-D-2 mixtures to 2-butyne and norbornene catalyzed by solutions of chlorotris(triphenylphosphine)rhodium(I), hydridocarbonyltris(triphenylphosphine)rhodium(I), and hydridotetrakis(5-phenyl-5-H-dibenzophosphole)rhodium(I)
by Lin, S. T.; Siegel, S.
The use of H-2/D-2 mixtures in place of H-2 as a probe of the mechanisms of hydrogenation is explored using the catalyst precursors chlorotris(triphenylphosphine)rhodium(I) (II), hydridocarbonyltris(triphenylphosphine)rhodium(I) (II), and hydridotetrakis(5-phenyl-5-H-dibenzophosphole)rhodium (I) (III). Benzene solutions of these complexes catalyze the H-2-D-2 equilibration, the relative rates decreasing in the order III > II > I. The accepted mechanism of hydrogenation catalyzed by I does not accommodate the observed isotopic exchange, which is inhibited by added acids (trifluoroethanol, 1,3,4-trichlorophenol) and accelerated by small amounts of triethylamine; the formation of hydridotris(triphenylphosphine)rhodium(l) is implicated. The H-2 and D, added to an unsaturated hydrocarbon is randomized with complexes II and III as the catalyst, whereas the molecular identity of H-2 and D, is retained if the dihydrido is the catalyst.
- Journal
- Kinetics and Catalysis
- Volume
- 46
- Issue
- 6
- Year
- 2005
- Start Page
- 844-852
- URL
- https://dx.doi.org/10.1007/s10975-005-0146-0
- ISBN/ISSN
- 1608-3210; 0023-1584
- DOI
- 10.1007/s10975-005-0146-0