Active O,Npy,N-Titanium(Ⅳ) Fluoride Precatalysts for Ethylene Polymerization;Exploring Fluoride Effects on Polymer Properties and Catalytic Performance
To allow rapid screening, non-metallocene Group Ⅳ metal halide (e.g., Cl, Br) complexes bearing one or more chelating ligands are often used in conjunction with a suitable co-catalyst such an alkyl aluminum (e.g., methylaluminoxane (MAO)) to facilitate in-situ formation of the active catalyst through a combined alkylation and abstraction process.By contrast, related metal-fluoride precatalysts have received scant attention for this application.1 The comparative difficulty in synthesizing such fluorocontaining complexes in sufficient purity may, in part, explain this dearth of reported catalytic investigations.Nevertheless, thermodynamic considerations regarding their catalytic activation raise some intriguing possibilities when put in comparison with their chloride counterparts.For instance, the bond enthalpies for Ti-F and Ti-Cl bonds are 569 and 494 kJ mol～, respectively, thus implying that an alkyl-aluminum promoted abstraction of a titanium fluoride should be less facile than abstraction of a chloride ligand.On the other hand, the bond enthalpies of Al-X bond differs more significantly (X =Cl 511 kJ mol-1 vs.F 663 kJ mol-1) suggesting that the resultant Al-F bond forming step should present a considerable driving force.
Gregory A.Solan
Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom;Institute of Chemistry,Chinese Academy of Sciences, Beijing 100190, China
国际会议
9th International Symposium on High-Tech Polymer Materials(第9届国际高技术高分子材料学术会议)(HTPM-9)
郑州
英文
6-6
2016-07-11（万方平台首次上网日期，不代表论文的发表时间）