Isotope Effects on Hydrogen Atom Transfer from Transition Metals to Carbon

Autor:	Graham P. Abramo, and Brian P. Santora, Kathryn E. Darula, David L. Ramage, Jack R. Norton, Mikhail A. Rodkin
Rok vydání:	1999
Předmět:	Hydrogen Organic Chemistry Inorganic chemistry chemistry.chemical_element Hydrogen atom Inorganic Chemistry Reaction rate constant chemistry Deuterium Atom Kinetic isotope effect Thermochemistry Physical chemistry Osmium Physical and Theoretical Chemistry
Zdroj:	Organometallics. 18:1106-1109
ISSN:	1520-6041 0276-7333
DOI:	10.1021/om980917v
Popis:	The isotope effect for transfer of a hydrogen/deuterium atom from HMn(CO)5/DMn(CO)5 to the monomeric trityl radical (p-tBu-C6H4)3C• (1) has been measured from −40 to +60 °C in toluene; the isotope effect for transfer from H2Os(CO)4/D2Os(CO)4 has been measured from 30 to 60 °C. Iterative kinetic simulation has been used to correct measured D• rate constants for the effects of incomplete deuteration. The isotope effect kH/kD at 25 °C is 3.18(3) for HMn(CO)5 and 4.3(3) for H2Os(CO)4. The larger isotope effect in the osmium case may be due to the difference in thermochemistry; the H−Os bond is stronger than the H−Mn one, and H• transfer from H2Os(CO)4 to 1 is approximately thermoneutral and in that sense “symmetric”.
Databáze:	OpenAIRE
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