Control of Fine Structure of Group IVb and VB Metals By the Template Function of Silica and Invention of New Reaction Systems

将Ti、Zr和Nb加入到二氧化硅四面体基体中，并借助于二氧化硅的模板作用控制它们的配位状态。XAFS分析表明，低Ti含量二氧化钛样品中的Ti处于四面体（Td）环境，高Ti含量二氧化钛样品中的Ti处于八面体（Oh）环境。以过氧化叔丁基为氧化剂，Td-Ti对辛-1-烯生成环氧化物表现出较高的活性。通过在二氧化钛表面引入氧，观察了超氧化物离子的EPR谱。在Td-Ti上形成的超氧化物的g值与Oh-Ti上形成的超氧化物的g值不同，Ti含量对这些光谱的影响与XAFS分析的结果相似。因此，XAFS技术很好地反映了二氧化钛的表面状态。少量掺入二氧化硅基体的Zr和Nb也呈td构型，对环氧化物的生成具有活性。因此，液相环氧化通常在反应的第一步通过过氧化氢与配位不饱和金属离子的配位进行。

Ti, Zr, and Nb were incorporated into the silica tetrahedral matrix, and their coordination state was controlled with an aid of the template action of the silica.XAFS analysis revealed that the Ti in titania-silica with low Ti content was in the tetrahedral (Td) environment and that in the high Ti content sample in the octahedral (Oh) environment. Td-Ti exhibited high activity to produce epoxide from oct-1-ene using t-butyl hydroperoxide as an oxidant. EPR spectra of superoxide oxide ion were observed by introducing oxygen on the surface of titania-silica. The g-value of the superoxide formed on Td-Ti was different from that on Oh-Ti and the effect of Ti content on these spectra was similar to that observed by the XAFS analysis. Thus XAFS technique well reflects the surface state of the titania-silica.Zr and Nb incorporated into silica matrix with a small amount level also took Td-configuration and was active for epoxide formation. Thus, the liquid-phase epoxidation generally proceeds through the coordination of hydroperoxide to the coordinatively unsaturated metal ion in the first step of the reaction.