http://www.paper.edu.cn 708 Macromol. Rapid Commun. 2001, 22, 708–709 Communication: Ethylene was polymerized with cycloalkylidene-bridged cyclopentadienyl metallocene catalysts 1–9 in the presence of methyl aluminoxane (MAO) as the cocatalyst. Unlike the normal titanocene catalysts, the cycloalkylidene-bridged cyclopentadienyl titanocene catalysts show much higher activities than the corresponding zirconocene and hafnocene catalysts and show the highest activities at higher temperature. This Chemical structures of the metallocenes. indicates that the cycloalkylidene-bridged cyclopentadie- nyl titanocene system is very thermally stable and maybe a very promising catalyst system for industrial applica- tion. Ethylene Polymerization with Cycloalkylidene-Bridged Cyclopentadienyl Metallocene Catalysts Shansheng Xu,1 Xiaobin Deng,1 Baiquan Wang,*1 Xiuzhong Zhou,1 Ling Yang,2 Yufei Li,2 Youliang Hu,2 Fenglou Zou,3 Yang Li3 1 The State Key Laboratory of Functional Polymer Materials for Adsorption and Separation, Department of Chemistry, Nankai University, Tianjin 300071, P.R. China; Laboratory of Organometallic Chemistry, Chinese Academy of Science Fax: 86-22-23502458; E-mail: [email protected] 2 Institute of Chemistry, Chinese Academy of Science, Beijing 100080, P.R. China 3 Research Institute of Beijing Yanshan Petrochemical Corporation, SINOPEC, Beijing 102550, P.R. China Introduction Cycloalkylidene-bridged cyclopentadienyl group 4 metal- locenes have been synthesized by the reaction of dilithiated ansa-Metallocene catalysts have been one of the most cycloalkylidene-bridged cyclopentadiene with MCl N 2 THF [1 – 4] 4 active research topics for about twenty years. Various in THF.a types of ring-bridged cyclopentadienyl and indenyl MAO was prepared from Al2(SO4)3 N 18 H2O and metallocenes have been studied and it has been found trimethylaluminium according to the usual manner.[5] that the activity and the stereoselectivity of olefin poly- Polymerizations were carried out in a 250-mL glass reac- merization reactions can be significantly affected by tor with a magnetic stirring bar at about 780 mmHg. Toluene slight structural variations of the bridging group in metal- (100 mL) was introduced into the reactor, the temperature locene catalysts.[3, 4] It is now generally recognized that was increased to the polymerization temperature, and then zirconocene catalysts exhibit higher activities than titano- the toluene was saturated with ethylene. A prescribed cenes and hafnocenes in olefin polymerization.[3] In this amount of MAO and a given metallocene dissolved in study, the properties of ethylene polymerization under the toluene were injected into the reactor, and then the polymer- ization was started. The polymerization was stopped by add- same polymerization conditions with a series of cycloalk- ing 100 mL of methanolic hydrochloric acid solution. The ylidene-bridged cyclopentadienyl group 4 metallocene polymer product was washed with ethanol and dried in vacuo catalysts in the presence of MAO are investigated. at 608C. The molecular weight of the polyethylene (PE) was meas- ured in decalin solution using an AVS 300 viscometer at 135 Experimental Part l 0.18C. All operations were carried out under a pure nitrogen atmos- phere using standard Schlenk techniques. Toluene and tetra- hydrofuran (THF) were purified by refluxing over a sodium/ (C6H5)2CO system under nitrogen. Polymerization grade ethylene (Yanshan Petrochem. Co., China) was used without a The syntheses and structures of cycloalkylidene-bridged cy- further purification. clopentadienyl metallocenes will be published elsewhere. Macromol. Rapid Commun. 2001, 22, No. 9 i WILEY-VCH Verlag GmbH, D-69451 Weinheim 2001 1022-1336/2001/0906–0708$17.50+.50/0 转载 中国科技论文在线 http://www.paper.edu.cn Ethylene Polymerization with Cycloalkylidene-Bridged Cyclopentadienyl Metallocene Catalysts 709 Table 1. The results of ethylene polymerization catalyzed with complexes 1–9. Polymerization conditions: Al/M = 2500, tempera- ture = 608C, monomer pressure = 1atm, in 100 mL toluene. For 1–3: monomer concentration = 3.0610 – 7 m, time = 15min; for 4–9: monomer concentration = 1.0610 – 6 m, time = 30min. Catalyst 1 2 3 4 5 6 7 8 9 Activitya) 9.10 37.4 19.5 0.46 1.00 1.40 0.03 0.02 0.30 a) Activity is in (kg PE) N (mmol M) – 1 N h – 1. nocenes and hafnocenes.[3, 4] The results can be explained if the presence of cycloalkylidene bridges increases the thermal stabilities of the titanocenes. Detailed studies of the effects of cycloalkylidene bridges on the catalytic activities of titanocenes are being continued in our group. From Table 2 it can see that the cyclopentene-bridged Scheme 1. Chemical structures of the metallocenes. cyclopentadienyl titanocene 1 has the highest activity at lower temperature (408C), but that the cyclohexene- Results and Discussion bridged cyclopentadienyl titanocene 2 has the highest The results of ethylene polymerization obtained with activity at higher temperature (608C). This may be due to metallocenes 1–9 activated by MAO are listed in Table 1 the fact that complex 1 has greater ring rigidity and lower and Table 2. thermal stability than 2 and 3. For the cycloheptene- The results show that the cycloalkylidene-bridged bridged cyclopentadienyl titanocene 3, in our polymeriza- cyclopentadienyl group 4 metallocenes 1–9 have very tion conditions, the activity increases with temperature to different activities for ethylene polymerization (Table 1). a maximum activity at 708C. This indicates that 3 is very Similar to many analogues,[3, 4] the zirconocenes show thermally stable and does not deactivate even at higher higher activities than hafnocenes. To our surprise the temperatures. Complex 3 has the highest activity cycloalkylidene-bridged cyclopentadienyl titanocenes 1– (A2.336107 (g PE) N (mol Ti) – 1 N h – 1) at 708C and 3 exhibit remarkably higher activities (up to above. It may be a very promising catalytic system for 3.746107 (g PE) N (mol Ti) – 1 N h – 1) than the correspond- industrial applications. ing zirconocenes and hafnocenes. In general, bridged and unbridged zirconocenes show higher activities than tita- Acknowledgement: The authors appreciate the support of NSFC(29734142), SINOPEC Visiting Scholar Foundation of Table 2. Ethylene polymerization with titanocenes/MAO at State, Key Lab in University and the State Key Laboratory of various temperatures. Polymerization conditions: Al/Ti = 2500, Elemento-Organic Chemistry. monomer pressure = 1atm, in 100 mL toluene, monomer con- centration = 3.0610 – 7 m, time = 15min. Received: January 2, 2001 aÞ b) cÞ Revised: April 6, 2001 Catalyst Tp Yield Activity Mg C g 6105 [1] H. Sinn, W. Kaminsky, Adv. Organomet. Chem. 1980, 18, 30 0.65 15.0 3.30 99. 40 0.68 27.0 2.85 [2] K. B. Sinclair, R. B. Wilson, Chem. Ind. 1994, 7, 857. 1 50 0.93 12.3 2.16 [3] [3a] R. F. Jordan, Adv. Organomet. Chem. 1991, 32, 325; 60 2.02 9.10 2.12 [3b] R. L. Halterman, Chem. Rev. 1992, 92, 965; [3c] W. 70 1.12 8.70 1.46 Kaminsky, Catal. Today 1994, 20, 257; [3d] P. C. 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Chem. 1999, 579, 24. c) — – 1 Mg: in g N mol , determined by viscosity in decahydro- [5] E. Gianetti, G. M. Nicoletti, R. Mazzochi, J. Polym. Sci., naphthalene at 1358C. Polym. Chem. Ed. 1995, 23, 2117..