Comparative Nucleophilic Displacement Reactions at Phorphorus and Silicon

在这个项目中，无机，生物无机和 有机化学程序，罗伯特R。福尔摩斯 马萨诸塞州大学将调查 其中磷和硅的亲核置换 反应由共同的基础描述。的研究 这些元素的取代反应机制涉及到一个 广泛的相关问题，如磷酰基转移 生物过程中的反应和聚合 硅烷醇和硅酸盐形成硅酸盐和硅氧烷。 这个问题将通过一个结合实验和 理论方法，导致确定 可能的中间体的能量学和立体化学 这些过程。理论程序包括从头算 分子轨道计算，并将处理常见的 亲核取代反应， 入境、出境和不出境的群体各不相同。的 实验方案涉及合成和结构 五配位阴离子硅酸盐的表征 作为五（烷氧基）-、五（羟基）-和五卤代-硅酸盐， 以及混合的烷基卤-、烷氧基羟基-和氯氟- 五取代的硅酸盐。单晶X射线结构 分析和固态核磁共振 将进行测量以确定结构变化 固体和溶液状态之间的关系，并评估 配体交换过程的活化能。

In this project funded within the Inorganic, Bioinorganic and Organometallic Chemistry Program, Robert R. Holmes of the University of Massachusetts will investigate the extent to which phosphorus and silicon nucleophilic displacement reactions are described by a common basis. The study of the substitution reaction mechanisms of these elements relates to a wide range of relevant problems such as phosphoryl transfer reactions in biological processes and the polymerization of silanols and siliconates to form silicates and silicones. The problem will be studied by a combined experimental and theoretical approach which leads to the determination of the energetics and stereochemistry of the likely intermediates in these processes. The theoretical program consists of ab-initio molecular orbital calculations and will treat common nucleophilic displacement reactions for which a series of entering, leaving and non-departing groups are varied. The experimental program involves the synthesis and structural characterization of five-coordinated anionic siliconates such as penta(alkoxy)- ,penta(hydroxy)- and pentahalo-siliconates as well as mixed alkylhalo-, alkoxyhydroxy- and chlorofluoro- penta-substituted siliconates. Single crystal X-ray structural analysis and solid state nuclear magnetic resonance measurements will be conducted to determine structural change between the solid and solution states and to evaluate activation energies for ligand exchange processes.