Jezequel M, Dufaud V, Ruiz-Garcia M J, Carrillo-Hermosilla F, Neugebauer U, Niccolai G P, Lefebvre F, Bayard F, Corker J, Fiddy S, Evans J, Broyer J P, Malinge J, Basset J M
Laboratoire de Chimie Organométallique de Surface, UMR 9986, CNRS-CPE Lyon, 43 Boulevard du 11 Novembre 1918, 69616 Villeurbanne Cédex, France.
J Am Chem Soc. 2001 Apr 18;123(15):3520-40. doi: 10.1021/ja000682q.
The reactions of CpZr(CH(3))(3), 1, and Cp(2)Zr(CH(3))(2), 2, with partially dehydroxylated silica, silica-alumina, and alumina surfaces have been carried out with careful identification of the resulting surface organometallic complexes in order to probe the relationship between catalyst structure and polymerization activity. The characterization of the supported complexes has been achieved in most cases by in situ infrared spectroscopy, surface microanalysis, qualitative and quantitative analysis of evolved gases during surface reactions with labeled surface, solid state (1)H and (13)C NMR using (13)C-enriched compounds, and EXAFS. 1 and 2 react with silica(500) and silica-alumina(500) by simple protonolysis of one Zr-Me bond by surface silanols with formation of a single well-defined neutral compound. In the case of silica-alumina, a fraction of the supported complexes exhibits some interactions with electronically unsaturated surface aluminum sites. 1 and 2 also react with the hydroxyl groups of gamma-alumina(500), leading to several surface structures. Correlation between EXAFS and (13)C NMR data suggests, in short, two main surface structures having different environments for the methyl group: Al-OZrCp(CH(3))(2) and Al-OZrCp(CH(3))(mu-CH(3))-[Al] for the monoCp series and Al-OZrCp(2)(CH(3)) and [Al]-OZrCp(2)(mu-CH(3))-[Al] for the bisCp series. Ethylene polymerization has been carried out with all the supported complexes under various reaction conditions. Silica-supported catalysts in the absence of any cocatalyst exhibited no activity whatsoever for ethylene polymerization. When the oxide contained Lewis acidic sites, the resulting surface species were active. The activity, although improved by the presence of additional cocatalysts, remained very low by comparison with that of the homogeneous metallocene systems. This trend has been interpreted on the basis of various possible parameters, including the (p-pi)-(d-pi) back-donation of surface oxygen atoms to the zirconium center.
已对CpZr(CH(3))(3)（1）和Cp(2)Zr(CH(3))(2)（2）与部分脱羟基的二氧化硅、硅铝酸盐和氧化铝表面的反应进行了研究，并仔细鉴定了生成的表面有机金属配合物，以探究催化剂结构与聚合活性之间的关系。在大多数情况下，通过原位红外光谱、表面微分析、与标记表面进行表面反应期间逸出气体的定性和定量分析、使用富含(13)C的化合物进行固态(1)H和(13)C NMR以及EXAFS来实现对负载型配合物的表征。1和2通过表面硅醇对一个Zr-Me键进行简单的质子解反应与二氧化硅(500)和硅铝酸盐(500)反应，形成单一明确的中性化合物。对于硅铝酸盐，一部分负载型配合物与电子不饱和的表面铝位点表现出一些相互作用。1和2也与γ-氧化铝(500)的羟基反应，产生几种表面结构。简而言之，EXAFS和(13)C NMR数据之间的相关性表明，对于单Cp系列，甲基具有不同环境的两种主要表面结构：Al-OZrCp(CH(3))(2)和Al-OZrCp(CH(3))(μ-CH(3))-[Al]；对于双Cp系列，为Al-OZrCp(2)(CH(3))和[Al]-OZrCp(2)(μ-CH(3))-[Al]。已在各种反应条件下用所有负载型配合物进行了乙烯聚合反应。在没有任何助催化剂的情况下，二氧化硅负载的催化剂对乙烯聚合没有任何活性。当氧化物含有路易斯酸性位点时，生成的表面物种具有活性。尽管通过添加额外的助催化剂活性有所提高，但与均相茂金属体系相比，活性仍然非常低。已根据各种可能的参数对这种趋势进行了解释，包括表面氧原子向锆中心的(p-π)-(d-π)反馈配位。
