化学反应的几何分析 I:动态堆积模型研究

本文首次提出了化学反应过程中几何可能性的定量研究.在下列条件下:(1)反应过程中,惰性配位体的键长,立体角系数等参数保持不变;(2)惰性配位体的压缩性很小;(3)在不压缩其它配位体的条件下,某一配位体在配位球面漂移所需的活化能低于这一配位体所形成的化学键断裂时所需的相应能量.我们提出动态堆积模型.以此来模拟反应过程中各个配位体间的相对位置和运动、配位体之间间隙的大小与受压缩的程度,并计算在反应中间过程中能够容纳新的配位体的最大空缺.考虑到使惰性配位体压缩将产生很大的空间势垒,以UCp3X为例说明了Lewis碱的配合与解离;金属-碳σ键的热分解以及一氧化碳插入反应的可能性.

Geometrical analysis of reaction pathways I: Study of reaction transition state by cone packing model dynamic approach

Geometrical conditions are analyzed in a study of metal complex substitution reaction mechanisms. By assuming SAF(dynamic) = SAF(static) for reaction substrates, gaps between reaction substrates, which are normally hard and inpenetrable, remaining almost non-neg. during the reaction, and an activation energy for bond migration around the unit sphere surface considerably lower than that needed in bond breaking, a dynamic cone packing approach is developed which describes quant. the relative positions and gaps between ligands during the reaction. The model can also be used to calculate the max. empty space for incoming ligands and for reaction intermediate. Reaction routes which leads to large neg. gaps between inert ligands simply imply high reaction barriers and they are thus unfavorable. Lewis base association and dissociation, metal-carbon s bond thermolysis, and CO insertion reaction are discussed briefly by using U(C5H5)3X (X = NCS-, Cl- and R-) as examples.4