Computational investigations into hydrogen-atom abstraction from rhodium hydride complexes by methyl radicals in aqueous solution

Jason M. Keith, Dan Meyerstein, Michael B. Hall

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1 Scopus citations

Abstract

The controversy in the reported kinetics for the hydrogen-atom abstraction reaction by methyl radicals for cis- and trans-[(Cyclam)RhIIIHCl] + and trans-[(Cyclam)(H2O)RhIIIH]2+ has been resolved by studying several feasible mechanistic pathways with density functional theory. The only low-energy reaction mechanism predicted by these calculations involves a single-step radical-propagation mechanism in which the methyl radical simply abstracts the Rh bound H atom from the complex to form methane and the reduced Rh product. Previous experimental work on the chloride and aquo complexes suggested contradictory kinetic isotope effect (KIE) values of 0.66±0.30 and 1.42±0.07 as well as rate constants for the reaction differing by four orders of magnitude. The calculated mechanism predicts a KIE value of 1.08 and a high reaction rate. The alternative mechanisms are described briefly. The controversy in the reported kinetics for the hydrogen-atom abstraction reaction bymethyl radicals for cis- and trans-[(Cyclam)RhIIIHCl]+ and trans-[(Cyclam)(H 2O)RhIIIH]2+ has been resolved by studying several feasible mechanistic pathways with density functional theory.

Original languageEnglish
Pages (from-to)4901-4905
Number of pages5
JournalEuropean Journal of Inorganic Chemistry
Issue number31
DOIs
StatePublished - 1 Nov 2011

Keywords

  • Density functional calculations
  • Kinetics
  • Radical reactions
  • Rhodium

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