Yan Xiuli, Ge Hongyu, Yang Xinzheng
Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry , Chinese Academy of Sciences , Beijing 100190 , People's Republic of China.
University of Chinese Academy of Sciences , Beijing 100049 , People's Republic of China.
Inorg Chem. 2019 May 6;58(9):5494-5502. doi: 10.1021/acs.inorgchem.8b03214. Epub 2019 Apr 26.
A direct hydride transfer mechanism with three cascade cycles for the conversion of carbon dioxide and dihydrogen to methanol (CO + 3H → CHOH + HO) catalyzed by a half-sandwich cobalt complex [CpCo(bpy-Me)OH] (1) is proposed based on density functional theory calculations. The formation of methanediol via hydride transfer from Co to formic acid (4 → TS) is the rate-determining step with a total barrier of 26.0 kcal/mol in free energy. Furthermore, 15 analogues of 1 are constructed by replacing the hydrogen atoms at the two meta and para positions of the bipyridine ligand with different functional groups (1b-1l), the carbon atoms in the bipyridine ligand with nitrogen atoms (1m-1o), and one pyridine ligand with N-heterocyclic carbene (1p). Among all newly proposed complexes, [CpCo(2,2'-bipyrazine)OH] (1n) is the most active one with a total barrier of 19.6 kcal/mol in free energy. Such a low barrier indicates 1n is a promising catalyst for efficient conversion of CO and H to methanol at room temperature.
基于密度泛函理论计算，提出了一种由半夹心钴配合物[CpCo(bpy-Me)OH] (1)催化二氧化碳和氢气转化为甲醇（CO₂ + 3H₂ → CH₃OH + H₂O）的具有三个级联循环的直接氢化物转移机制。通过氢化物从Co转移到甲酸形成甲二醇（4 → TS）是速率决定步骤，自由能总势垒为26.0 kcal/mol。此外，通过用不同官能团取代联吡啶配体两个间位和对位的氢原子（1b - 1l）、将联吡啶配体中的碳原子替换为氮原子（1m - 1o）以及用N-杂环卡宾取代一个吡啶配体（1p），构建了1的15种类似物。在所有新提出的配合物中，[CpCo(2,2'-联吡嗪)OH] (1n)是活性最高的，自由能总势垒为19.6 kcal/mol。如此低的势垒表明1n是在室温下将CO₂和H₂高效转化为甲醇的有前景的催化剂。
