期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 18, 期 32, 页码 9870-9876出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201201042
关键词
carbon dioxide fixation; density functional calculations; epoxides; polyoxometalates; radical reactions
资金
- National Natural Science Foundation of China [20731002, 21173021, 21103010]
- 111 Project [B07012]
- Program of Cooperation of the Beijing Education Commission [20091739006]
- Beijing Municipal Science & Technology Commission [Z09010300820902]
- Excellent Young Scholars Research Fund of Beijing Institute of Technolog [2010Y1214]
- Basic Research Fund of Beijing Institute of Technology [20101742032]
CoII-substituted a-Keggin-type 12-tungstenphosphate [(n- C4H9)4N]4H[PW11Co(H2O)O39]- (PW11Co) is synthesized and used as a single-component, solvent-free catalyst in the cycloaddition reaction of CO2 and epoxides to form cyclic carbonates. The mechanism of the cycloaddition reaction is investigated using DFT calculations, which provides the first computational study of the catalytic cycle of polyoxometalate-catalyzed CO2 coupling reactions. The reaction occurs through a single-electron transfer from the doublet CoII catalyst to the epoxide and forms a doublet CoIIIcarbon radical intermediate. Subsequent CO2 addition forms the cyclic carbonate product. The existence of radical intermediates is supported by free-radical termination experiments. Finally, it is exhilarating to observe that the calculated overall reaction barrier (30.5 kcal?mol-1) is in good agreement with the real reaction rate (83 h-1) determined in the present experiments (at 150?degrees C).
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