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>Catalytic activation of ethylene C-H bonds on uniform d(8) Ir(I) and Ni(II) cations in zeolites: toward molecular level understanding of ethylene polymerization on heterogeneous catalysts
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Catalytic activation of ethylene C-H bonds on uniform d(8) Ir(I) and Ni(II) cations in zeolites: toward molecular level understanding of ethylene polymerization on heterogeneous catalysts
The homolytic activation of the strong CH bonds in ethylene is demonstrated, for the first time, on d(8) Ir(I) and Ni(II) single atoms in the cationic positions of zeolites H-FAU and H-BEA under ambient conditions. The oxidative addition of C2H4 to the metal center occurs with the formation of a d(6) metal vinyl hydride, explaining the initiation of the olefin-polymerization cycle on d(8) M(I/II) sites in the absence of pre-existing M-H bonds. Under mild reaction conditions (80-220 degrees C, 1 bar), the catalytic dimerization to butenes and dehydrogenative coupling of ethylene to butadiene occurs over these catalysts. 1-Butene is not converted to butadiene under the reaction conditions applied. Post-reaction characterization of the two materials reveals that the active metal cations remain site-isolated whereas deactivation occurs due to the formation of carbonaceous deposits on the zeolites. Our findings have significant implications for the molecular level understanding of ethylene conversion and the development of new ways to functionalize C-H bonds under mild conditions.
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机译：均裂的激活强有力的CH债券乙烯是证明,第一次d(8)红外(I)和镍(II)单个原子阳离子的位置沸石H-FAU H-BEA在环境条件下。C2H4金属中心发生的d(6)形成金属氢化物乙烯,解释的起始烯烃聚合周期d (8) M (I / II)的网站在没有预先存在的mh债券。温和的反应条件(80 - 220摄氏度,1酒吧),催化二聚丁烯和dehydrogenative耦合乙烯丁二烯发生在这些催化剂。下转换为丁二烯的反应应用条件。两种材料显示的特征活性金属阳离子依然存在site-isolated而失活发生原因碳质沉积的形成上沸石。对分子水平上的影响理解转换和乙烯发展新方法用碳氢键债券在温和的条件下。
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