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A theoretical study of the photochemistry of methylcopper hydride. Activation of the carbon‐hydrogen bond
Author(s) -
Castillo S.,
Poulain E.,
Novaro O.
Publication year - 2009
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560360853
Subject(s) - chemistry , copper , hydride , photoexcitation , ab initio , methane , hydrogen , atom (system on chip) , computational chemistry , photochemistry , atomic physics , excited state , organic chemistry , physics , computer science , embedded system
An ab initio study of the interaction between methane and a copper atom is performed by means of extensive configuration interaction (CI) calculations framed within the effective core approximation. The geometrical structures of reactants, intermediate species, and products were all optimized and various reaction pathways analyzed which strongly favor the reaction channel: Cu + CH 4 → HCuCH 3 → CuH + CH 3 . It is found that the interaction of methane with the metal is efficiently induced by copper photoexcitation in the energy range that corresponds to the Cu( 2 S) → Cu( 2 P) transition. The overall reaction proceeds via five HCuCH 3 ( 2 A') intermediate states where copper is inserted in the C—H bond and whose energy is determined to be lower than that of the reactants Cu( 2 P) + CH 4 ( 1 A'). The lowest reaction pathway leads to a HCu + CH 3 final state which remains 25 kcal/mol above the lowest intermediate species, without any activation barrier. The other possible final state CuCH 3 + H is only 4 kcal/mol above the CuH + CH 3 , but is reached only after surmounting a very high barrier of 52 kcal/mol. The present results appear to be in complete agreement with the experimental facts and even explain some of the recorded data which hitherto no theoretical model has been able to substantiate.