THEORETICAL-STUDY OF THE CYCLOPROPANE RING-OPENING BY PALLADIUM(II) COMPLEXES
THEORETICAL-STUDY OF THE CYCLOPROPANE RING-OPENING BY PALLADIUM(II) COMPLEXES
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DOI：
10.1021/ja00249a004
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发表时间：
1987-07-22
影响因子：
15
通讯作者：
BACKVALL, JE
中科院分区：
文献类型：
--
作者：
BLOMBERG, MRA;SIEGBAHN, PEM;BACKVALL, JE
用CASSCF和压缩Cl方法计算了不同钯化合物（PdCl_2、PdCl_（42-）和PdCl ~+）对环丙烷的开环反应。研究了两种反应机理，角活化和边缘活化。将结果与以前的无配体钯（0）原子与环丙烷反应的研究进行了比较，正如预期的那样，发现氯化物配体的加入大大改变了反应势垒。对于钯（O），仅边缘活化具有低活化能。对于钯（II）络合物，只有PdCl+的角活化具有低活化能，估计为约5 kcal/mol。对于PdCl 2和PdCl 42-，发现对于角和边缘激活都具有非常高的势垒（25-45 kcal/mol）。研究发现，配合物之间的能量差与钯原子态的激发能直接相关。络合物中钯的原子状态由共价键的实际数量和钯的实际电荷决定。钯的原子状态反映在计算的4d布居中。本文的研究结果对钯（II）催化环丙烷开环反应提出了新的看法：角活化，而不是通常公认的边活化，被预测为最有利的反应途径。
CASSCF and contracted Cl calculations have been performed on the ring opening of cyclopropane by different palladium (II) compounds (PdCl2, PdCl42-, and PdCl+). Two reaction mechanisms were studied, corner activation and edge activation. The results are compared to a previous study of the reaction of the ligand-free palladium (0) atom with cyclopropane, and, as expected, it was found that the addition of the chloride ligands changes the reaction barriersdrastically. For palladium (O) only the edge activation has a low activation energy. For the palladium (II) complexes only the corner activation by PdCl+ has a low activation energy, estimated to be about 5 kcal/mol. For PdCl2 and PdCl42" very high barriers (25-45 kcal/mol) are found for both corner and edge activation. The energy differences between the complexes investigated are found to be directly relatedto the excitation energies of the atomic states of palladium involved. The atomic state of palladium involved in a complex is determined by the actual number of covalent bonds, and the actual charge of palladium. The atomic state is reflected in the calculated 4d populationof palladium. The results obtained in this paper lead to a new view on the ring opening of cyclopropane by palladium (II): corner activation, rather than the usually accepted edge activation, is predicted to be the most favorable reaction pathway.