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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Systematic Investigation of Electronic and Molecular Structures for the First Transition Metal Series Metallocenes M(C_5H_5)_2 (M = V, Cr, Mn, Fe, Co, and Ni)
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Systematic Investigation of Electronic and Molecular Structures for the First Transition Metal Series Metallocenes M(C_5H_5)_2 (M = V, Cr, Mn, Fe, Co, and Ni)

机译：对第一过渡金属系列茂金属M（C_5H_5）_2（M = V，Cr，Mn，Fe，Co和Ni）的电子和分子结构的系统研究

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The electronic structures of the first-row transition-metal metallocenes, MCp_2 (M = V, Cr, Mn, Fe, Co, and Ni), have been studied using a broad range of density functional methods with flexible double-ζ plus polarization (DZP) basis sets. Geometrical parameters of the D_(5h) and D_(5d) conformations (and structures of lower symmetry for CrCp_2 and CoCp_2) were fully optimized. For the ferrocene system, best characterized experimentally, the B3LYP, BLYP, and BP86 methods give structures in good agreement with experiment. For the D_(5h)-D_(5d) energy difference, the same three methods predict 0.75 kcal/mol (B3LYP), 0.99 kcal/mol (BLYP), and 1.13 kcal/mol (BP86). The cyclopentadienyl rings are very nearly planar; the angles of the C-H bond out of the Cp ring are less than 1° for all metallocenes except ferrocene. The C-H bonds are bent slightly away from the metal for V and Mn, slightly toward the metal for Fe and Ni, and virtually not at all from chromocene. According to the energetic and vibrational analyses, the D_(5h) conformations are found to be the global minima, leaving open the possibility that the D_(5d) conformations may exist under certain conditions. However, MnCp_2 probably exists as a mixture of both D_(5h) and D_(5d) conformations, because both are genuine minima with only a small energy difference. The predicted B3LYP energy differences (D_(5h)-D_(5d)) for the six metallocenes are 0.29 (V), 0.28 (Cr), 0.13 (Mn), 0.75 (Fe), 0.38 (Co), and 0.23 kcal/mol (Ni). A number of reassignments of experimental vibrational bands are suggested. The molecular orbital energy level diagrams and the electron configurations for the metallocenes are compared. This information, obtained in a consistent manner across the first transition metal series, is helpful for discussion of the bonding characters and the chemical reactivities of these metallocenes.
机译：第一行过渡金属茂金属MCp_2（M = V，Cr，Mn，Fe，Co和Ni）的电子结构已通过多种密度泛函方法进行了研究，这些方法具有灵活的double-ζ加极化功能（ DZP）基础集。完全优化了D_（5h）和D_（5d）构型的几何参数（以及CrCp_2和CoCp_2的对称性较低的结构）。对于二茂铁体系，最好通过实验表征，B3LYP，BLYP和BP86方法给出的结构与实验吻合良好。对于D_（5h）-D_（5d）能量差，相同的三种方法预测0.75 kcal / mol（B3LYP），0.99 kcal / mol（BLYP）和1.13 kcal / mol（BP86）。环戊二烯基环几乎是平面的。对于除二茂铁外的所有茂金属，C-H键从Cp环外的角度均小于1°。对于V和Mn，C-H键略微远离金属弯曲，对于Fe和Ni，C-H键略微朝向金属弯曲，而实际上几乎没有二茂铬。根据能量和振动分析，发现D_（5h）构型是全局最小值，这使得D_（5d）构型在某些条件下可能存在的可能性悬而未决。但是，MnCp_2可能以D_（5h）和D_（5d）构象的混合物形式存在，因为两者都是真正的极小值，且能量差很小。六个茂金属的预测B3LYP能量差（D_（5h）-D_（5d））为0.29（V），0.28（Cr），0.13（Mn），0.75（Fe），0.38（Co）和0.23 kcal /摩尔（镍）。建议对实验振动带进行许多重新分配。比较了茂金属的分子轨道能级图和电子构型。在第一过渡金属系列中以一致的方式获得的该信息有助于讨论这些茂金属的键合特性和化学反应性。

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