ESR法研究烯烃岐化反应中钨(Ⅵ)催化剂价态的变化

ESR STUDY ON THE VALENCE CHANGE OF W(Ⅵ) CATALYSTS IN THE METATHESIS OF OLEFINS

在烯烃及其衍生物的均相岐化反应中,催化剂过渡金属价态的变化是尚未完全清楚的问题.近年来报导了应用ESR研究环烯的开环聚合及WCl_6固载在高分子载体上烯烃岐化反应中钨(Ⅵ)价态的变化.我们应用ESR研究了正链烯烃及其衍生物在岐化反应中钨价态的变化,得到了一些有启发性的ESR信号. ESR测量采用JES-FEIXG电子自旋共振仪在X波段工作.锰标作为磁场标尺和相对定量的内标.温度的控制与测量采用ES-DVTI变温附件.

WC16 contacted with 1-hexene exhibits an ESR signal with 5 = 2.006 Hpp= 1.25mT, which is assigned to hydrocarbon radical species,and the same fact is observed in the reaction of WC16 with Me4Sn. Four distinct ESR signals are recorded during the reaction of 1-hexene with WC16-Me4Sn-cyclohexane system. Three ESR signals are observed in the reaction of methyl oleate with WCl6-Me4Sn-cyclohexane system and two signals appear in the reaction of WCl4(2,6-C6H3Cl2O)2-Me4Sn-cyclohexane system with 1-hexene. The correlation of the observed signals to the active species of the catalysts is proposed.