Metal and Ligand Effects on Coordinated Methane pKa: Direct Correlation with the Methane Activation Barrier
Metal and Ligand Effects on Coordinated Methane pKa: Direct Correlation with the Methane Activation Barrier
复制标题
金属和配体对协调甲烷 pKa 的影响：与甲烷活化势垒的直接相关性
DOI：
10.1021/acs.jpca.0c04756
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发表时间：
2020
影响因子：
--
通讯作者：
Amy S. Guan, Ivy X.
中科院分区：
文献类型：
--
作者：
Amy S. Guan, Ivy X.
用密度泛函理论和耦合簇方法研究了3d金属和配体对配位甲烷C-H键的酸性和活化性的影响。在配位甲烷的pKaf和随后H3C-H活化的自由能垒(ΔG⧧)之间建立了强烈的、直接的关系。这一关系的少数异常值表明了影响甲烷活化势垒的其他显著因素(如产物的热力学稳定性和配体-金属配位类型)。活化势垒和pKavue的变化很大，前者为34.8kcal/mol，后者为28.6pka单位。还得出了特定金属和配体之间的明显趋势；金属离子，如CoI，以及Lewis酸和π-酸，始终使连接的甲烷产生更高的酸度，因此ΔG⧧较低。
DFT and coupled cluster methods were used to investigate the impact of 3d metals and ligands upon the acidity and activation of coordinated methane C–H bonds. A strong, direct relationship was established between the pKaof coordinated methane and the free energy barriers (ΔG⧧) to subsequent H3C–H activation. The few outliers to this relationship indicated other salient factors (such as thermodynamic stability of the product and ligand–metal coordination type) that impacted the methane activation barrier. High variations in the activation barriers and pKavalues were found with a range of 34.8 kcal/mol for the former and 28.6 pKaunits for the latter. Clear trends among specific metals and ligands were also derived; metal ions such as CoI, as well as Lewis acids and π-acids, consistently yielded higher acidity for ligated methane and hence lower ΔG⧧.