Anastasi Anna E, Deeth Robert J
Inorganic Computational Chemistry Group, Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K.
J Chem Theory Comput. 2009 Sep 8;5(9):2339-52. doi: 10.1021/ct9001569.
Molecular modeling of coordination complexes continues to present challenges for force field methods. Implicit or explicit treatment of the significant d electron effects is mandatory. Ligand field molecular mechanics is designed for coordination complexes by explicitly including the ligand field stabilization energy (LFSE) and it is applied here to model the trans influence in tetracoordinate Pt(II) complexes of general formulas PtX4, PtX3Y, cis-PtX2Y2, and trans-PtX2Y2, where X and Y are OH2, H(-), Cl(-), Br(-), PR3, SH2, NR3, and pyridine. Parameters have been developed within the Merck molecular force field using DFT structures and energies as reference data. Both geometric changes and relative energies are generally well-reproduced although PH3 and H(-) complexes show deviations. However, for phosphine complexes, replacing PH3 with PMe3 resolves all bar one of these. The LFSE associated with the low-spin d(8) configuration ensures planar coordination and provides an electronic connection between all the ligands, thus enabling a correct description of the trans influence. The parameters developed for NR3 and PR3 with R = H work well for R = Me and Et and, in agreement with experimental and/or DFT structures, display either a tetrahedral distortion or even ligand dissociation.
配位络合物的分子建模对于力场方法而言仍然是一项挑战。必须对显著的d电子效应进行隐式或显式处理。配体场分子力学通过明确纳入配体场稳定能（LFSE）来设计用于配位络合物，并且在此处应用于对通式为PtX4、PtX3Y、顺式-PtX2Y2和反式-PtX2Y2的四配位Pt(II)络合物中的反位影响进行建模，其中X和Y为OH2、H(-)、Cl(-)、Br(-)、PR3、SH2、NR3和吡啶。已在默克分子力场内利用DFT结构和能量作为参考数据开发了参数。尽管PH3和H(-)络合物存在偏差，但几何变化和相对能量总体上都能得到很好的再现。然而，对于膦络合物，用PMe3取代PH3可以解决除一个之外的所有问题。与低自旋d(8)构型相关的LFSE确保平面配位，并在所有配体之间提供电子连接，从而能够正确描述反位影响。为R = H的NR3和PR3开发的参数对于R = Me和Et也适用，并且与实验和/或DFT结构一致，显示出四面体畸变甚至配体解离。
