Study of Catalytic Conversion of Organosilicon Compounds

尽管人们对碳氢化合物的催化反应进行了大量的研究，但对有机硅烷的转化进行的研究工作却很少，尽管有机硅烷在各个领域的应用越来越重要。在实验室和工业中，有机硅烷的反应通常使用金属卤化物和过渡金属配合物在均相液相中进行。硅化合物在多相催化中的基础化学研究是一个非常有吸引力和重要的挑战。因此对烷基硅烷的歧化反应和烷基化反应进行了研究。对于二乙基硅烷（E2）和二乙基二甲基硅烷（E2M2）的歧化反应，只有强酸性催化剂SiO_2-Al_2O_3 （SA）、氧化铝和硫酸化ZrO_2 （SO_3/ZrO_2）表现出较高的活性。在弱酸性催化剂上进行了裂化反应。尽管不平衡反应仅在较低的反应温度下发生，但无论反应物和催化剂如何，反应温度的升高都会导致裂化反应的增加。有机硅烷在SiO_2-Al_2O_3和SO_3/ZrO_2上的相对反应活性依次为E2M2>E2，在氧化铝上的相对反应活性依次为E2>E2M2。这有力地表明，不同类型的机制是有效的；氢化物萃取和质子加成分别是Al_2O_3和SO_3/ZrO_2反应的起始步骤。在固体超强酸SO_3/ZrO_2催化剂上，E2与丙烯、1-丁烯、顺式-2-丁烯、异丁烯、1,3-丁二烯和甲基乙炔等烯烃顺利发生烷基化反应。无论使用何种类型的烯烃，均以正烷基化产物为主，异烷基化产物次之。这表明反应是通过烯烃对硅离子的亲核攻击而发生的。有趣的是，产物分布与过渡金属配合物催化的硅氢化反应基本相同。这是国际上首次发现有机硅化合物的非均相催化转化。少

Although numerous works on catalytic reactions of hydrocarbons have been done, only few research works have been carried out on transformations of organosilanes, in spite of an increasing importance of their application to various fields. Both in laboratories and industries, reactions of organosilane are usually performed in a homogeneous liquid phase using metal halides and transition metal complexes. The development of fundamental chemistries of Si compounds in heterogeneous catalysis is quite attractive and important challenge.Hence the disproportionation and the alkylation of alkylsilanes were examined.1.Dispropotionation of alkylsialnesFor the disproportionation reaction of diethylsilane (E2) and diethyldimethylsilane (E2M2), only strongly acidic catalysts, SiO_2-Al_2O_3 (SA), alumina and sulfated ZrO_2 (SO_3/ZrO_2), exhibited high activities. On weakly acidic catalysts a cracking reaction was operative. Although the dispropotionation reaction was only the reaction at lower reacti … More on temperatures, an increase of reaction temperature resulted in the increase of the cracking reaction regardless the reactants and the catalysts.The relative reactivity of organosilanes was in the order of E2M2>E2 on SiO_2-Al_2O_3 and SO_3/ZrO_2, while the order on alumina was found to be E2>E2M2. This strongly suggests that differnt types of mechanisms are operative ; a hydride abstraction and a proton addition are the initiation step of the reaction over Al_2O_3 and SO_3/ZrO_2, respectively.2.Alkylation of alkylsilanesThe alkylation of E2 with olefins such as propene, 1-butene, cis-2-butene, isobutene, 1,3-butadiene and methylacetylene smoothly took place over an SO_3/ZrO_2 catalyst which is known as a solid superacid. n-Alkylated products were the main products and the iso-alkylated ones were the minor products regardless the type of olefins used. This suggests that the reaction takes place via nucleophilic attack of olefins on a silicocation.It is interesting finding that the product distribution is basically the same as that of the hydrosilylation catalyzed by transition metal complexes.These result is a first finding of the heterogeneous catalytic conversion of organosilicone compounds in the world. Less