STEREOCHEMISTRY OF DISCRETE 8-COORDINATION .1. BASIC ANALYSIS
STEREOCHEMISTRY OF DISCRETE 8-COORDINATION .1. BASIC ANALYSIS
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DOI：
10.1021/ic50006a001
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发表时间：
1963-01-01
影响因子：
4.6
通讯作者：
SILVERTON, JV
中科院分区：
文献类型：
--
作者：
HOARD, JL;SILVERTON, JV
通过将有用的理论与利用全三维分析的x射线研究的精确立体化学数据相结合，获得了一种对离散八配位具有有用预测能力的有序模式。这个“现象学理论”最全面的结论是，对于十二面体（Mo (CN) s~ 4型）和方形反棱镜构型（图1和2），直接键相互作用的能量学差异必须很小，以至于它们之间的选择通常或总是由其他因素决定。实际配合物配位基的详细形状绝不是硬球模型的形状，而是使闭合壳相互作用的配体排斥能达到（约束）最小的形状；最有利的十二面体和反棱镜形状（表1）同样能很好地实现这一点。对于四齿双齿螯合物，似乎：(1)竞争立体异构体的闭壳排斥能的差异可以很容易地达到5千卡/摩尔，(2)当配合物带电时，内部库仑排斥的最小化优先。详细讨论了M (IV)/3-二酮螯合物M (X2) 4的立体异构现象。复杂性的增加，如配体的混合，多齿性，通常是更好地服务于十二面体配位。Mo (CN) s-4离子受到特别关注。
An ordered pattern having useful predictive capacity for discrete eight-coordination is obtained by interweaving helpful bits of theory with accurate stereochemical data from X-ray studies2 utilizing full three-dimensional analysis. The most sweeping conclusion of this" phenomenological theory” is that the energetics of direct bonding interaction must differ so little for the dodecahedral (Mo (CN) s~ 4-type) andsquare antiprismatic configurations (Fig. 1 and 2) that the choice between them is determined, usually or always, by other factors. The detailed shape of the coordination group of a real complex is never that of the hard sphere model, but is rather that which makes the ligand repulsive energy from closed-shell inter-actions a (constrained) minimum; the most favorable dodecahedral and antiprismatic shapes (Table I) accomplish this equally well. For a tetrakis-bidentate chelate it appears (1) that differences in the closed-shell repulsive energy for com-peting stereoisomers may run easily to 5 kcal./mole,(2) that minimization of internal coulombic repulsions takes preced-ence when the complex is charged. Stereoisomerism in the M (IV)/3-diketo chelates, M (X2) 4, is discussed in detail. Increasing complication, eg, mixing of ligands, multidentate character, usually is better served by dodecahedral coordination. The Mo (CN) s-4 ion receives special attention.