Dihydride transfer: a bimolecular mechanism in the isomerization of cis-dihydridobromo(carbonyl)[bis(diphenylphosphino)ethane]iridium, IrH2Br(CO)(dppe)

Autor:	John A. Maguire, Curtis E. Johnson, William D. Jones, Richard Eisenberg, Amanda J. Kunin
Rok vydání:	1987
Předmět:	Reaction mechanism Addition reaction Chemistry chemistry.chemical_element General Chemistry Photochemistry Biochemistry Oxidative addition Catalysis Chemical kinetics Elimination reaction Colloid and Surface Chemistry Reaction rate constant Iridium Isomerization
Zdroj:	Journal of the American Chemical Society. 109:2963-2968
ISSN:	1520-5126 0002-7863
DOI:	10.1021/ja00244a018
Popis:	The oxidative addition of H2 to IrBr(CO) (doppe), 2, (dppe - 1,2-bis(diphenyphosphino)ethane) yields a kinetic dihydride species, 3, which then isomerizes to a more stable isomer 4. This isomerizatoin of 3 to 4 has been studied kinetically as a function of initial H2 pressure. Two pathways are operative at ambient temperature. The first is a reductive elimation/oxidative addition sequence which is first order in complex, while the second is a bimolecular pathway involving dihydride transfer from 3 to 20 to produce 4 and regenerate 2. The dihydride transfer pathway is second order in complex and becomes the dominant isomerizatoin mechanism when less than one equivalent of H2 relative to 2 has been added to the system. All of the kinetic data have been fit to a complete rate law which leads to a bimolecular rate constant for dihydride transfer of 0.21/M.min. Below -20C, the dhydride transfer pathway for isomerization is the only one operating.
Databáze:	OpenAIRE
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