Heterolytic Activation of C–H Bonds on CrIII–O Surface Sites Is a Key Step in Catalytic Polymerization of Ethylene and Dehydrogenation of Propane

摘要: We describe the reactivity of well-defined chromium silicates toward ethylene and propane. The initial motivation for this study was to obtain a molecular understanding Phillips polymerization catalyst. catalyst contains reduced sites on silica catalyzes without activators or preformed Cr–C bond. CrII are commonly proposed active in synthesized characterized chromium(II) found that these materials, slightly contaminated with minor amount CrIII sites, have poor activity few sites. In contrast, chromium(III) 1 order magnitude higher activity. initiate by activation C–H bond ethylene. Density functional theory analysis process showed step is heterolytic corresponds σ-bond metathesis type process. same sili...