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Theoretical study on the gas‐phase reaction mechanism between palladium monoxide and methane
Author(s) -
Yang HuaQing,
Hu ChangWei,
Gao Chao,
Yang MengYao,
Li FangMing,
Li CaiQin,
Li XiangYuan
Publication year - 2011
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.21926
Subject(s) - chemistry , singlet state , carbon monoxide , reaction mechanism , monoxide , palladium , reaction rate constant , activation energy , photochemistry , methane , medicinal chemistry , computational chemistry , catalysis , kinetics , inorganic chemistry , organic chemistry , excited state , physics , quantum mechanics , nuclear physics
The gas‐phase reaction mechanism between palladium monoxide and methane has been theoretically investigated on the singlet and triplet state potential energy surfaces (PESs) at the CCSD(T)/AVTZ//B3LYP/6‐311+G(2d, 2p), SDD level. The major reaction channel leads to the products PdCH 2 + H 2 O, whereas the minor channel results in the products Pd + CH 3 OH, CH 2 OPd + H 2 , and PdOH + CH 3 . The minimum energy reaction pathway for the formation of main products (PdCH 2 + H 2 O), involving one spin inversion, prefers to start at the triplet state PES and afterward proceed along the singlet state PES, where both CH 3 PdOH and CH 3 Pd(O)H are the critical intermediates. Furthermore, the rate‐determining step is RS‐CH 3 PdOH → RS‐2‐TS1cb → RS‐CH 2 Pd(H)OH with the rate constant of k = 1.48 × 10 12 exp(−93,930/ RT ). For the first CH bond cleavage, both the activation strain Δ E ≠ strain and the stabilizing interaction Δ E ≠ int affect the activation energy Δ E ≠ , with Δ E ≠ int in favor of the direct oxidative insertion. On the other hand, in the PdCH 2 + H 2 O reaction, the main products are Pd + CH 3 OH, and CH 3 PdOH is the energetically preferred intermediate. In the CH 2 OPd + H 2 reaction, the main products are Pd + CH 3 OH with the energetically preferred intermediate H 2 PdOCH 2 . In the Pd + CH 3 OH reaction, the main products are CH 2 OPd + H 2 , and H 2 PdOCH 2 is the energetically predominant intermediate. The intermediates, PdCH 2 , H 2 PdCO, and t‐HPdCHO are energetically preferred in the PdC + H 2 , PdCO + H 2 , and H 2 Pd + CO reactions, respectively. Besides, PdO toward methane activation exhibits higher reaction efficiency than the atom Pd and its first‐row congener NiO. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011