Mechanistic Study of Methanol Oxidation by RuIV-oxo complexes
Mechanistic Study of Methanol Oxidation by RuIV-oxo complexes
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RuIV-氧配合物氧化甲醇的机理研究
DOI：
10.1142/s1088424615500285
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发表时间：
2015
影响因子：
1.5
通讯作者：
K. Yoshizawa
中科院分区：
文献类型：
--
作者：
Y. Shiota;S. Takahashi;S. Ohzu;T. Ishizuka;T. Kojima;K. Yoshizawa
用密度泛函理论方法研究了Ruivo(Tpa)(tpa=三(2-吡啶甲基)胺)(1a)、Ruivo(6-coo-tpa)(6-coo-tpa=2-(6-carboxyl-pyridyl)methyl-bis(2-pyridylmethyl)amine)(1b)和Ruivo(N4Py)(N4Py=N，N-bis(2-pyridyl-methyl)-N-bis(2-pyridyl)methylamine)(1c))三种非卟啉Ru配合物催化甲醇合成甲醛的反应。相对于第一次从甲基(路径1)和羟基(路径2)抽氢，甲醇氧化成甲醛有两条可能的反应路径。路径1和路径2分别涉及羟甲基自由基(·CH2OH)和甲氧基(CH3O·)作为中间体。密度泛函理论计算表明，在三个RuIV-oxo络合物的反应中，这两条路径具有能量可比性。与1a和1are的反应分别由C-H键解离引发，活化势垒分别为22.2kcal/mol和21.4kcal/mol，而与1bis的反应由O-H键解离引发，活化能垒为18.1kcal/mol。然而，计算表明，在所有的反应途径中，决定反应速率的步骤都是从甲醇的CH3基团中提取H原子。这些结果与RuIV-oxo络合物反应的动力学分析相一致，有助于探讨甲醇氧化反应的机理。
The catalytic conversion of methanol to formaldehyde by three kinds of non-porphyrin Ru complexes, RuIVO(TPA) (TPA = tris(2-pyridylmethyl)amine) (1a), RuIVO(6-COO-TPA) (6-COO-TPA = 2-(6-carboxyl-pyridyl)methyl-bis(2-pyridylmethyl)amine) (1b), and RuIVO(N4Py) (N4Py = N,N-bis(2-pyridyl-methyl)-N-bis(2-pyridyl)methylamine) (1c), is discussed by using density functional theory (DFT) calculations. There are two possible reaction pathways for the oxidation of methanol to formaldehyde with respect to the first hydrogen abstraction from the methyl group (path 1) and the hydroxyl group (path 2). Path 1 and path 2 involve the hydroxymethyl radical (•CH2OH) and the methoxyl radical (CH3O•), respectively, as an intermediate. DFT calculations demonstrate that the two pathways are energetically comparable in the reactions by the three RuIV–oxo complexes. The reactions with1aand1care initiated by the C–H bond dissociation with activation barriers of 22.2 and 21.4 kcal/mol, respectively, while the reaction with1bis initiated by the O–H bond dissociation with an activation barrier of 18.1 kcal/mol. However, the calculations showed that the rate-determining step is the H-atom abstraction from the CH3group of methanol in all the pathways. These results are in good agreement with kinetic analysis of the reactions by the RuIV–oxo complexes, being useful for considering the mechanism of methanol oxidation.