Ab initio potential energy surface and electron correlation effect in CH activation of CH sub 4 by coordinatively unsaturated RhCl(PH sub 3 ) sub 2
- Institute for Molecular Science, Okazaki (Japan)
Ab initio molecular orbital (MO) study of a model CH activation reaction, oxidative addition of CH{sub 4} to coordinatively unsaturated RhCl(PH{sub 3}){sub 2}, is presented. We have found that the reaction proceeds through a bifurcated ({eta}{sup 2}) CH{sub 4} complex, (CH{sub 4})RhCl(PH{sub 3}){sub 2}, and a three-centered transition state. At the highest level of calculation, MP4SDTQ, the reaction is exothermic by 24 kcal/mol relative to the isolated reactants and by 7 kcal/mol relative to the CH{sub 4} complex from which the activation barrier required is 3 kcal/mol. The CH{sub 4} complex is stabilized by the CH {yields} Rh d donation supplemented significantly by Rh {yields} CH{sub 4} back-donation as well as intermolecular (dispersion) and intramolecular electron correlation. The electron correlation is found to change the heat of reaction by 37 kcal/mol, thus shifting the location of transition state earlier and lowering the activation barrier drastically.
- OSTI ID:
- 6537319
- Journal Information:
- Journal of Physical Chemistry; (USA), Journal Name: Journal of Physical Chemistry; (USA) Vol. 94:14; ISSN 0022-3654; ISSN JPCHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
033000* -- Natural Gas-- Properties & Composition
ALKANES
CALCULATION METHODS
CATALYSTS
CHEMICAL ACTIVATION
COMPLEXES
CORRELATIONS
ELECTRON CORRELATION
HYDROCARBONS
MATHEMATICAL MODELS
METHANE
MOLECULAR ORBITAL METHOD
ORGANIC COMPOUNDS
RHODIUM COMPLEXES
TRANSITION ELEMENT COMPLEXES