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Development of Catalysts for Epoxidation of Olefins

烯烃环氧化催化剂的研制

基本信息

批准号：
61850154
负责人：
MATSUDA Yoshihisa
金额：
$ 4.29万
依托单位：
Kyushu University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1988
项目状态：
已结题

项目摘要

Niobium(V) and molybdenum(V) porphyrins were prepared. Molybdenum complexes had an octahedral structure with an oxo and an alkoxo ligand on their axial site, while tri-u-oxo dimer of niobium(V) porphyrins had cis-hepta-coordinated one. Complexes catalyzed photochemical epoxidation of olefins in benzene upon aerobic irradiation of with visible light. Photochemical reactions of above complexes were followed by means of visible absorption and ESR spectroscopy.Nionium(V) and molybdenum(V) porphyrins were reduced in benzene upon anaerobic irradiation with visible light affording corresponding pentacoordinate complexes. Homolysis of an axial coordination bond took place during the photoreduction and axial ligands were released as corresponding radical species. The reduced complexes were oxidized in benzene by molecular oxygen upon aeration resuting superoxide complexes. The superoxide complexes transferred an oxygen atom to an olefin added in the soultion to form corresponding epoxide.The photoreduction of the complexes was revealed by means of time-resolved ESR spectroscopy. The photoreduction, the homolysis of the axial coordination bond, proceeded via a charge transfer triplet state and a triplet pair of a radical and a reduced central metal. The superoxide complex was formed by reaction of molecular oxygen with the triplet pair. Addition of molecules which could coordinate at the axial site of the complexes disturbed the formation of the superoxide complexes.No cis-trans isomerization took place in the photo-epoxidation process suggesting an ionic nature of the intermediate. Olefins having a terminal double bond showed lower activity than ones having an internal duble bond. Olefins with more alkyl substituent groups had higher activity than those with less substituent groups. Introduction of picket fence type substituents into the porphyrin ligand improved both activity and selectivity.

制备了铌（V）和钼（V）卟啉。钼配合物为八面体结构，轴位上有一个氧代和一个烷氧基配体，而铌（V）卟啉的三-氧代二聚体为顺式七配位。可见光有氧照射下配合物催化烯烃在苯中的光化学环氧化反应。用可见光吸收光谱和电子自旋共振（ESR）光谱研究了上述配合物的光化学反应，发现在苯中，NiO 2（V）和MoO 2（V）卟啉在可见光下被还原，得到相应的五配位配合物。轴向配位键的均裂发生在光还原和轴向配体释放相应的自由基物种。还原态的配合物在苯中被分子氧氧化，产生超氧配合物。超氧化物配合物将氧原子转移到溶液中加入的烯烃上形成相应的环氧化物，用时间分辨ESR谱研究了配合物的光还原反应。光还原，轴向配位键的均裂，进行通过电荷转移三重态和一个自由基和一个减少的中心金属的三重态对。超氧配合物是由分子氧与三重态对反应形成的。在配合物的轴向位置上添加配位的分子干扰了超氧配合物的形成，在光环氧化过程中没有发生顺反异构化反应，表明中间体的离子性质。具有末端双键的烯烃比具有内部双键的烯烃表现出更低的活性。烷基取代基多的烯烃比烷基取代基少的烯烃活性高。在卟啉配体中引入栅栏型取代基，提高了活性和选择性。