INOR 191 |
| The structures, energies, kinetics and mechanism for the intra- and intermolecular transformation of acetylene to vinylidene were studied in the imidazolylphosphine rhodium(I) complexes RhCl(iPr2PIm')2(RCCH) where Im' = 1-methyl-4-t-butyl-imidazol-2-yl. Kinetic studies showed that the conversion of alkyne complex is much faster (20-40 times) for RhCl(iPr2PIm')2(RCCH) than that for RhCl(iPr2PPh)2(RCCH). Thus, the heterocyclic substituent clearly accelerates the conversion. Further studies to clarify the role of the heterocycle will be presented. Spectral data for doubly 13C-labeled alkynes and complexes will be presented in an effort to probe the interaction of metal fragment and coordinated alkyne or vinylidene. Ab initio MO studies calculated optimized structures and energies for reactants, products, and intermediates at the Hartree-Fock and MP2 levels of theory. The activation energies for the isomerization of alkyne π-complex to hydrido-alkynyl intermediate were computed to be relatively low (16.0 kcal/mol) compared to that of an intramolecular 1,2-shift (33.7 kcal/mol). Bimolecular mechanisms for the hydrogen shift will also be discussed.
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Organometallic General and Catalysis
7:00 PM-9:00 PM, Sunday, 13 March 2005 Convention Center -- Hall D, Poster
Sci-Mix
Division of Inorganic Chemistry |
