Chinese Journal of Catalysis ›› 2017, Vol. 38 ›› Issue (4): 736-744.DOI: 10.1016/S1872-2067(17)62802-X

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Transformation of carbon dioxide into valuable chemicals over bifunctional metallosalen catalysts bearing quaternary phosphonium salts

Wuying Zhanga,b, Rongchang Luoa, Qihang Xua, Yaju Chena, Xiaowei Lina, Xiantai Zhouc, Hongbing Jia   

  1. a School of Chemistry, Key Laboratory of Low-Carbon Chemistry & Energy Conservation of Guangdong Province, Sun Yat-sen University, Guangzhou 510275, Guangdong, China;
    b School of Applied Chemistry and Biological Technology, Shenzhen Polytechnic, Shenzhen 518055, Guangdong, China;
    c School of Chemical Engineering and Technology, Sun Yat-sen University, Zhuhai 519000, Guangdong, China
  • Received:2017-01-17 Revised:2017-02-28 Online:2017-04-18 Published:2017-04-12
  • Supported by:

    This work was supported by the National Natural Science Foundation of China (21676306, 21425627), the National Key Research and Development Program of China (2016YFA0602900), and the Natural Science Foundation of Guangdong Province (2016A030310211, 2015A030313104).

Abstract:

The chemical transformation of CO2 under mild conditions remains a great challenge because of its exceptional kinetic and thermodynamic stability. Two important reactions in the transformation of CO2 are the N-formylation reaction of amines using hydrosilanes and CO2, and the cycloaddition of CO2 to epoxides. Here, we report the high efficiency of bifunctional metallosalen complexes bearing quaternary phosphonium salts in catalyzing both of these reactions under solvent-free, mild conditions without the need for co-catalysts. The catalysts' bifunctionality is attributed to an intramolecular cooperative process between the metal center and the halogen anion. Depending on the reaction, this activates CO2 by permitting either the synergistic activation of Si-H bond via metal-hydrogen coordinative bond (M-H) or the dual activation of epoxide via metal-oxygen coordinative bond (M-O). The one-component catalysts are also shown to be easily recovered and reused five times without significant loss of activity or selectivity. The current results are combined with previous work in the area to propose the relevant reaction mechanisms.

Key words: Carbon dioxide, Salen catalyst, Quaternary phosphonium salt, Cooperative effect, Reaction mechanism