A DFT Study of the Mechanism of the Spontaneous Activation of H2by Ni, Pd, Pt, and Pd2
A DFT Study of the Mechanism of the Spontaneous Activation of H2by Ni, Pd, Pt, and Pd2
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Ni、Pd、Pt 和 Pd2 自发活化 H2 机理的 DFT 研究
DOI：
10.1021/jp027519x
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发表时间：
2003
影响因子：
2.9
通讯作者：
C. Minot
中科院分区：
文献类型：
--
作者：
M. Alikhani;C. Minot
用三参数泛函(B3LYP)方法计算了M：H2(M=Ni，Pd，Pt)化合物的1A1和3B2电子态的弯曲能谱.结果表明，对于镍和铂原子，σH-H键的活化可能导致二氢物种处于单重态；而对于Pd原子，则自发形成与Pd(1 S 0)+H2弱结合的Pd-H2络合物。在第一种情况下，从金属中心的三重态开始的相互作用与氢化物物种(3B2态)通过高势垒高度(分别为46.5千卡/摩尔和11.5千卡/摩尔)有关。体系间交叉有利于σH-H键在单重态(1A1)下的活化。对于帕金森病，另一种机制发生了。二氢化合物种可以从分子络合物(1A1)开始，通过一个轻微的吸热过程，通过低活化能(6kcal/mol)形成。对于基态为三重态的Pd2二聚体，H2的离解类似于Ni和铂原子的离解。该机制意味着单重态和三重态之间的系统间交叉。在交点后，提出了Pd-Pd-H2平面折叠的非平面机构。
The bending energy profiles of 1 A 1 and 3 B 2 electronic states have been calculated for the M:H 2 (M = Ni, Pd, and Pt) compounds using three parameters functional (B3LYP). It has been shown that the σ H - H -bond activation leading to the dihydride species in a singlet state is possible for the nickel and platinum atoms, while for Pd, the complex Pd-H 2 , weakly bound with respect to Pd( 1 S 0 ) + H 2 , is formed spontaneously. In the first case, Ni and Pt, the interaction beginning from the triplet state of the metal center correlates with the hydride species ( 3 B 2 state) after passing a high barrier height (46.5 and 11.5 kcal/mol, for Ni and Pt, respectively). An inter-system crossing favors the activation of the σ H - H -bond in the singlet state ( 1 A 1 ). For Pd, another mechanism occurs. The dihydride species may be formed starting from the molecular complex ( 1 A 1 ) by a slightly endothermic process through low activation energy (6 kcal/mol). For the Pd 2 dimer, whose ground state is a triplet state, the dissociation of H 2 is similar to that of the Ni and Pt atoms. The mechanism implies an inter-system crossing between the singlet and triplet states. After the crossing point, a nonplanar mechanism implying a folding of the Pd-Pd-H 2 planes is proposed.