Ruthenium(II)-Catalyzed Hydrogenation of Carbon Dioxide to Formic Acid. Theoretical Study of Significant Acceleration by Water Molecules
Ruthenium(II)-Catalyzed Hydrogenation of Carbon Dioxide to Formic Acid. Theoretical Study of Significant Acceleration by Water Molecules
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DOI：
10.1021/om060307s
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发表时间：
2006-06
期刊：
影响因子：
2.8
通讯作者：
Yu-ya Ohnishi;Y. Nakao;Hirofumi Sato;S. Sakaki
中科院分区：
文献类型：
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作者：
Yu-ya Ohnishi;Y. Nakao;Hirofumi Sato;S. Sakaki
采用密度泛函和MP4（SDQ）方法对钌催化二氧化碳加氢制甲酸进行了理论研究。在水分子存在下，反应进行如下：（1）CO2形成加合物cis-Ru（H）2（PMe 3）3（H2O）（CO2），其中CO2的C和O原子分别与H（氢化物）配体和H2O的H原子相互作用。(2)H配体对CO2的亲核攻击很容易发生，得到Ru-（η1-甲酸酯）中间体Ru（H）（PMe 3）3（η1-OCOH）（H2O），其活化势垒比CO2插入Ru−H键的活化势垒小得多，这是在没有水分子的情况下的速率决定步骤。(3)速率决定步骤是二氢分子与Ru-（η2-甲酸酯）络合物Ru（H）（PMe 3）3（η2-O2 CH）（H2O）的配位，其活化势垒小于CO2插入Ru−H键的活化势垒。(4)在Ru（H）（PMe 3）3（η1-OCOH）（H2）（H2O）中，Ru-（η1-甲酸根）部分容易与二氢分子发生复分解反应，生成了一个稳定的Ru（η1-甲酸根）.
Ru-catalyzed hydrogenation of carbon dioxide to formic acid was theoretically investigated with DFT and MP4(SDQ) methods. In the presence of water molecules, the reaction proceeds as follows: (1) Carbon dioxide forms the adduct cis-Ru(H)2(PMe3)3(H2O)(CO2), in which the C and O atoms of CO2 interact with the H (hydride) ligand and the H atom of H2O, respectively. (2) Nucleophilic attack of the H ligand to CO2 takes place easily to afford a Ru-(η1-formate) intermediate, Ru(H)(PMe3)3(η1-OCOH)(H2O), with a much smaller activation barrier than that of the CO2 insertion into the Ru−H bond, which is the rate-determining step in the absence of water molecules. (3) The rate-determining step is the coordination of a dihydrogen molecule with the Ru-(η2-formate) complex, Ru(H)(PMe3)3(η2-O2CH)(H2O), the activation barrier of which is smaller than that of the CO2 insertion into the Ru−H bond. (4) The metathesis of the Ru-(η1-fomate) moiety with the dihydrogen molecule easily occurs in Ru(H)(PMe3)3(η1-OCOH)(H2)(H2O) to...