酸性磷化合物萃取金属反应中取代基空间效应的分子力学研究

本文利用分子力学计算从理论上估算了酸性有机磷化合物萃取金属离子反应中取代基的空间效应。二烷基磷(膦)酸叔丁酯(Ⅱ)作为萃合物分子的近似模型结构。计算结果表明, 羟基氧在自由萃取剂Ⅰ和Ⅱ中的局部空间张力能之差与烷基的结构有密切的关系, 可近似地用来作为烷基空间效应的量度(E_(s,ex))。并用于一系列有机磷(膦)酸萃取Ni、Co为稀土的多元回归分析。结果表明, E_(s,ex)基本上反映了该萃取过程中的空间效应。

A Molecular Mechanics Study of Steric Effect of Substituents on Extraction of Metals by Acidic Phosphorus Esters

The molecular mechanics calculations (Allinger's MM2 program) was used to study the steric effect of substituents on extraction of metals (Ni, Co, RE) by acidic phosphorus esters. Some parameters for phosphorus which were not included in MM2 were estimated and used to reproduce the known structure of some phosphorus compounds with satisfactory results.For the evaluation of steric effect of substituents, dialkyl t-butyIphosphate or phosphinate (Ⅱ) was proposed as a model structure for the simulation of the simulation of the steric environment of complexes. The optimum geometry of (II) and phosphorus ester (I) were determined by molecular mechanics program. It was found that the difference of the local steric energy of hydroxyl oxygen in I and II is closely correlated with the degree of the size of substituents and can thus be used as a measurement of the steric effect of the substituents (E_(s,ex)). A series of E_(s,ex) of alkyl and alkoxyl were estimated and used in the multiple regression of extraction data.