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首页> 外文期刊>Coordination chemistry reviews >Covalency and chemical bonding in transition metal complexes: An ab initio based ligand field perspective
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Covalency and chemical bonding in transition metal complexes: An ab initio based ligand field perspective

机译：过渡金属配合物中的共价键和化学键：从头开始的配体场角度

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In this work, a general, user-friendly method - ab initio ligand field theory (AILFT), is described and illustrated. AILFT allows one to unambiguously extract all ligand field parameters (the ligand field one-electron matrix V-LFT, the Racah parameters B and C, and the spin-orbit coupling parameter zeta) from relatively straightforward multi-reference ab initio calculations. The method applies to mononuclear complexes in d(n) or f(n) configurations. The method is illustrated using complete active space self-consistent field (CASSCF) and N-electron valence perturbation theory (NEVPT2) calculations on a series of well documented octahedral complexes of Cr-III with simple ligands such as F , Cl , Br , I , NH3 and CN . It is shown that all well-known trends for the value of 10Dq (the spectrochemical series) are faithfully reproduced by AILFT. By comparison of B and zeta for Cr-III in these complexes with the parameters calculated for the free ion Cr3+, the covalency of the Cr-ligand bond can be assessed quantitatively (the non-relativistic and relativistic nephelauxetic effects). The variation of ligand field parameters for complexes of 3d, 4d and 5d elements is studied using MCl63 (M = Cr-III, Mo-III, W-III) as model examples. As reflected in variations of 10Dq, B and zeta across this series, metal-ligand covalency increases from CrCl63 to MoCl63 to WCl63. Using the angular overlap model, the one-electron parameters of the ligand field matrix are decomposed into increments for sigma- and pi-metal-ligand interactions. This allows for the quantification of variations in sigma- and pi-ligand donor properties of these ligands. Using these results, the well documented two-dimensional spectroscopic series for complexes of Cr-III is quantitatively reproduced. Comparison of the results obtained using CASSCF and NEVPT2 reveals the importance of dynamic electron correlation. Finally, the limitations of the AILFT method for complexes with increasing metal-ligand covalency are analyzed and discussed. (C) 2017 Elsevier B.V. All rights reserved.
机译：在这项工作中，描述并说明了一种通用的，用户友好的方法-从头算起的配体场论（AILFT）。 AILFT允许从相对简单的多参考从头算式中毫不含糊地提取所有配体场参数（配体场单电子矩阵V-LFT，Racah参数B和C以及自旋轨道耦合参数zeta）。该方法适用于d（n）或f（n）构型的单核络合物。使用完整的活性空间自洽场（CASSCF）和N电子价态扰动理论（NEVPT2）计算，对一系列已充分记录的Cr-III具有简单配体（如F，Cl，Br，I）的八面体配合物进行了说明。 ，NH3和CN。结果表明，AILFT忠实地再现了10Dq（光谱化学系列）价值的所有众所周知的趋势。通过将这些配合物中Cr-III的B和zeta与针对游离离子Cr3 +计算的参数进行比较，可以定量评估Cr-配体键的共价性（非相对论和相对论性肾上腺皮质激素作用）。以MCl63（M = Cr-III，Mo-III，W-III）为模型实例，研究了3d，4d和5d元素配合物的配体场参数变化。正如整个系列中10Dq，B和zeta的变化所反映的，金属配体的共价性从CrCl63到MoCl63到WCl63不断增加。使用角度重叠模型，将配体场矩阵的单电子参数分解为σ-和pi-金属-配体相互作用的增量。这允许量化这些配体的σ-和π-配体供体性质的变化。利用这些结果，可以定量地复制记录充分的Cr-III络合物的二维光谱系列。使用CASSCF和NEVPT2获得的结果的比较揭示了动态电子相关的重要性。最后，分析并讨论了AILFT方法对金属配体价增加的配合物的局限性。 （C）2017 Elsevier B.V.保留所有权利。

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