Valence and extra-valence orbitals in main group and transition metal bonding
Valence and extra-valence orbitals in main group and transition metal bonding
复制标题
DOI：
10.1002/jcc.20492
复制
发表时间：
2007-01-15
影响因子：
3
通讯作者：
Weinhold, F.
中科院分区：
文献类型：
--
作者：
Landis, C. R.;Weinhold, F.
我们解决了Masera和Morokuma最先提出的问题，即在自然原子/键轨道算法(NaOS，NBOS)和相关的自然布居分析中对空p轨道的有问题的处理。我们根据空p-集的两种替代处理所产生的数值误差(均方根密度偏差)来量化这个问题，这两种处理导致了不同的NaOS、原子电荷和理想化的Lewis结构表示。将这一标准应用于广泛的主族和过渡族物种的计算应用(使用单结构和多结构共振模型)，揭示了有趣的一般模式：(I)对于正价物种，相对不显著的差异，其中单一共振结构通常是足够的，但(Ii)标准NAO算法对于高价物种，明显的优越性，其中多共振特征明显。这些比较表明，过渡金属成键中存在分歧的“价壳扩展”问题是如何与相互竞争的超价态概念模型(即骨架杂化中的“p轨道参与”与3c/4e共振特征)密切相关的。这些结果为原子电荷的标准NAO计算以及主、过渡基团超价态的一般3C/4E(A：B-C双左箭头A-B：C共振)图的优劣提供了一个定量的量度。(C)2006年威利期刊公司。
We address the issue first raised by Maseras and Morokuma with regard to the questionable treatment of empty p-orbitals in the algorithm for natural atomic/bond orbitals (NAOs, NBOs) and associated natural population analysis. We quantify this issue in terms of the numerical error (root-mean-square density deviation) resulting from the two alternative treatments of empty p-sets, leading to distinct NAOs, atomic charges, and idealized Lewis structural representations. Computational application of this criterion to a broad spectrum of main group and transition group species (employing both single- and multi-structure resonance models) reveals the interesting general pattern of (i) relatively insignificant differences for normal-valent species, where a single resonance structure is usually adequate, but (ii) clear superiority of the standard NAO algorithm for hypervalent species, where multi-resonance character is pronounced. These comparisons show how the divisive issue of "valence shell expansion" in transition metal bonding is deeply linked to competing conceptual models of hypervalency (viz., "p-orbital participation" in skeletal hybridization vs. 3c/4e resonance character). The results provide a quantitative measure of superiority both for the standard NAO evaluation of atomic charges as well as the general 3c/4e (A: B-C double left right arrow A-B :C resonance) picture of main- and transition-group hypervalency. (C) 2006 Wiley Periodicals, Inc.