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The Kinetic Isotope Effect as a Probe of Spin Crossover in the CH Activation of Methane by the FeO + Cation
Author(s) -
Mai Binh Khanh,
Kim Yongho
Publication year - 2015
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201411309
Subject(s) - spin crossover , kinetic isotope effect , chemistry , kinetic energy , spin states , quantum tunnelling , reaction rate constant , activation energy , transition metal , potential energy , spin (aerodynamics) , reagent , computational chemistry , atomic physics , chemical physics , thermodynamics , kinetics , physics , inorganic chemistry , condensed matter physics , quantum mechanics , deuterium , catalysis , biochemistry
Abstract Two‐state reactivity (TSR) is often used to explain the reaction of transition‐metal–oxo reagents in the bare form or in the complex form. The evidence of the TSR model typically comes from quantum‐mechanical calculations for energy profiles with a spin crossover in the rate‐limiting step. To prove the TSR concept, kinetic profiles for CH activation by the FeO + cation were explored. A direct dynamics approach was used to generate potential energy surfaces of the sextet and quartet H‐transfers and rate constants and kinetic isotope effects (KIEs) were calculated using variational transition‐state theory including multidimensional tunneling. The minimum energy crossing point with very large spin–orbit coupling matrix element was very close to the intrinsic reaction paths of both sextet and quartet H‐transfers. Excellent agreement with experiments were obtained when the sextet reactant and quartet transition state were used with a spin crossover, which strongly support the TSR model.