Computational Studies Explain the Importance of Two Different Substituents on the Chelating Bis(amido) Ligand for Transfer Hydrogenation by Bifunctional Cp*Rh(III) Catalysts
Computational Studies Explain the Importance of Two Different Substituents on the Chelating Bis(amido) Ligand for Transfer Hydrogenation by Bifunctional Cp*Rh(III) Catalysts
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DOI：
10.1021/om500356e
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发表时间：
2014-06
期刊：
影响因子：
2.8
通讯作者：
A. Nova;David J. Taylor;A. Blacker;S. Duckett;R. Perutz;O. Eisenstein
中科院分区：
文献类型：
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作者：
A. Nova;David J. Taylor;A. Blacker;S. Duckett;R. Perutz;O. Eisenstein
使用计算方法（DFT-B3 PW 91）来解决先前的实验研究（Chem.Commun. 2009，6801），其显示当XNC 6 H4 NX ′ = TsNC 6 H4 NH时，在二氯甲烷中通过Et 3 N·HCO 2 H由16-电子双官能Cp*RhIII（XNC 6 H4 NX ′）催化的环状亚胺的转移氢化比当XNC 6 H4 NX ′ = HNC 6 H4 NH或TsNC 6 H4 NTs（Cp* = η5-C5 Me 5，Ts =甲苯磺酰基）时更快。计算研究还考虑了在低温下实验观察到的甲酸络合物的作用。采用Cp* 被Cp取代，Ts被苯磺酰基（Bs）取代的实验络合物模型，对气相体系的计算表明，甲酸脱氢生成CpRhIIIH（XNC 6 H4 NX ′H）是通过外层机理进行的. 16电子铑络合物+甲酸被证明是在平衡与甲酸络合物，但后者位于脱氢的途径之外。计算结果与实验结果一致，表明转移加氢反应是快速的。
A computational approach (DFT-B3PW91) is used to address previous experimental studies (Chem. Commun. 2009, 6801) that showed that transfer hydrogenation of a cyclic imine by Et3N·HCO2H in dichloromethane catalyzed by 16-electron bifunctional Cp*RhIII(XNC6H4NX′) is faster when XNC6H4NX′ = TsNC6H4NH than when XNC6H4NX′ = HNC6H4NH or TsNC6H4NTs (Cp* = η5-C5Me5, Ts = toluenesulfonyl). The computational study also considers the role of the formate complex observed experimentally at low temperature. Using a model of the experimental complex in which Cp* is replaced by Cp and Ts by benzenesulfonyl (Bs), the calculations for the systems in gas phase reveal that dehydrogenation of formic acid generates CpRhIIIH(XNC6H4NX′H) via an outer-sphere mechanism. The 16-electron Rh complex + formic acid are shown to be at equilibrium with the formate complex, but the latter lies outside the pathway for dehydrogenation. The calculations reproduce the experimental observation that the transfer hydrogenation reaction is faste...