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首页> 外文期刊>Chemistry: A European journal >Assessing metal-metal multiple bonds in Cr-Cr, Mo-Mo, and W-W compounds and a hypothetical U-U compound: A quantum chemical study comparing DFT and multireference methods
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Assessing metal-metal multiple bonds in Cr-Cr, Mo-Mo, and W-W compounds and a hypothetical U-U compound: A quantum chemical study comparing DFT and multireference methods

机译：评估Cr-Cr，Mo-Mo和W-W化合物以及假设的U-U化合物中的金属-金属多重键：比较DFT和多参考方法的量子化学研究

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To gain insights into the trends in metal-metal multiple bonding among the Group 6 elements, density functional theory has been employed in combination with multiconfigurational methods (CASSCF and CASPT2) to investigate a selection of bimetallic, multiply bonded compounds. For the compound [Ar-MM-Ar] (Ar=2,6-(C _6H _5) _2-C _6H _3, M=Cr, Mo, W) the effect of the Ar ligand on the M _2 core has been compared with the analogous [Ph-MM-Ph] (Ph=phenyl, M=Cr, Mo, W) compounds. A set of [M _2(dpa) _4] (dpa=2,2′-dipyridylamide, M=Cr, Mo, W, U) compounds has also been investigated. All of the compounds studied here show important multiconfigurational behavior. For the Mo _2 and W _2 compounds, the σ ~2π ~4δ ~2 configuration dominates the ground-state wavefunction, contributing at least 75 %. The Cr _2 compounds show a more nuanced electronic structure, with many configurations contributing to the ground state. For the Cr, Mo, and W compounds the electronic absorption spectra have been studied, combining density functional theory and multireference methods to make absorption feature assignments. In all cases, the main features observed in the visible spectra may be assigned as charge-transfer bands. For all compounds investigated the Mayer bond order (MBO) and the effective bond order (EBO) were calculated by density functional theory and CASSCF methods, respectively. The MBO and EBO values share a similar trend toward higher values at shorter normalized metal-metal bond lengths.
机译：为了深入了解第6组元素之间金属-金属多重键合的趋势，已将密度泛函理论与多构型方法（CASSCF和CASPT2）结合使用，以研究双金属多重键合化合物的选择。对于化合物[Ar-MM-Ar]（Ar = 2,6-（C _6H _5）_2-C _6H _3，M = Cr，Mo，W），比较了Ar配体对M _2核的影响与类似的[Ph-MM-Ph]（Ph =苯基，M = Cr，Mo，W）化合物。还研究了一组[M _2（dpa）_4]（dpa = 2,2'-联吡啶，M = Cr，Mo，W，U）化合物。本文研究的所有化合物均显示出重要的多构型行为。对于Mo _2和W _2化合物，σ〜2π〜4δ〜2构型主导基态波函数，贡献至少75％。 Cr _2化合物显示出更细微的电子结构，具有许多有助于基态的构型。对于Cr，Mo和W化合物，结合密度泛函理论和多参考方法对吸收光谱进行了研究，研究了电子吸收光谱。在所有情况下，可以将可见光谱中观察到的主要特征指定为电荷转移带。对于所有研究的化合物，分别通过密度泛函理论和CASSCF方法计算了Mayer键序（MBO）和有效键序（EBO）。在较短的标准化金属-金属键长度下，MBO和EBO值具有相似的趋势，即朝向更高的值。

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