Importance of Quantum Effects for C−H Bond Activation Reactions
Importance of Quantum Effects for C−H Bond Activation Reactions
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DOI：
10.1021/ja972209r
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发表时间：
1997-10
影响因子：
15
通讯作者：
J. Espinosa-García;J. Corchado;D. Truhlar
中科院分区：
文献类型：
--
作者：
J. Espinosa-García;J. Corchado;D. Truhlar
我们计算了trans-Rh（PH 3）2Cl（η2-CH 4）重排为Rh（PH 3）2ClH（CH 3）的反应速率常数，其中甲烷的C-H键被活化，Rh（I）被氧化为Rh（III），甲烷被裂解。量子零点能量包括在39个振动模式，激发振动态也被量子化，量子力学隧穿贡献包括多维小曲率隧穿近似。玻恩-奥本海默势能、反应路径几何和速率计算所需的振动频率都是使用直接动力学方法从密度泛函理论中获得的。在200 K时，用量子效应计算的速率常数比用经典力学计算的速率常数大194倍。包括量子化的振动能，但不包括隧穿，将这种差异减小到3.4倍。在150 K时，这些因子分别增加到2770和11，而在300 K时，这些因子分别减少到20和1.67。因此，t.
We calculate the reaction rate constant of the rearrangement of trans-Rh(PH3)2Cl(η2-CH4) to Rh(PH3)2ClH(CH3), in which the C−H bond of methane is activated, Rh(I) is oxidized to Rh(III), and methane is cleaved. Quantum zero point energy is included in 39 vibrational modes, excited vibrational states are also quantized, and quantum mechanical tunneling contributions are included by the multidimensional small-curvature tunneling approximation. Born−Oppenheimer potential energies, reaction-path geometries, and vibrational frequencies needed for the rate calculations are obtained from density functional theory using the direct dynamics approach. At 200 K the rate constant calculated with quantum effects is 194 times larger than the rate constant calculated using classical mechanics to describe the atomic motion. Including quantized vibrational energies but not tunneling reduces this discrepancy to a factor of 3.4. These factors are increased to 2770 and 11 at 150 K and decreased to 20 to 1.67 at 300 K. Thus t...