Journal of Organometallic Chemistry 627 (2001) 233 – 238 www.elsevier.nl/locate/jorganchem Synthesis of titanium trichloride complexes of 1,2,3-trisubstituted cyclopentadienyls and their use in styrene polymerization Bun Yeoul Lee a, * 1 , Jin Wook Han b , Hwimin Seo b , In Su Lee b , Young Keun Chung b, * 2 a Department of Molecular Science and Technology, Ajou Uniersity, Suwon 442 -749 South Korea b School of Chemistry and Center for Molecular Catalysis, College of Natural Sciences, Seoul National Uniersity, Seoul 151 -747, South Korea Received 15 June 2000; received in revised form 26 February 2001; accepted 27 February 2001 Abstract The synthesis, characterization and styrene polymerization properties of titanium trichloride compounds (5, 1,3-dimethyl-2-n - butylcyclopentadienyl; 6, 1,3-dimethyl-2-t -butylcyclopentadienyl; 13, 1,3-diphenyl-2-n -butylcyclopentadienyl; 14, 1,3-dimethyl-2- phenylcyclopentadienyl; 15, 1,2,3-triphenylcyclopentadienyl) containing 1,2,3-trisubstituted cyclopentadienyl ligands are reported. Reactions of lithiated cyclopentadienide with Me 3 SiCl followed by addition of TiCl 4 gave new titanium trichloride compounds 5 and 6, respectively, in reasonable yields, and reactions of cyclopentadiene with Ti(NMe 2 ) 4 followed by Me 3 SiCl or Me 2 SiCl 2 gave new titanium trichloride compounds 13 – 15, respectively, in reasonable yields. Compound 14 has been characterized by single crystal X-ray diffraction studies: monoclinic space group P 2 1 /c ; a =15.893(2), b =7.199(1), c =12.812(2) A  ,  =108.394(7)°, Z =4 and V =1390.9(3) A  3 . The catalytic behavior of the new titanium compounds in styrene polymerization has been studied in the presence of excess methylaluminoxane. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Cyclopentadienyl; Titanium; Styrene; Polymerization; Syndiotactic 1. Introduction Since Ishihara et al. reported the first preparation of syndiotactic polystyrene (s-PS) using the CpTiCl 3 /MAO catalyst system [1,2], a wide variety of new catalytic systems based on titanium or zirconium compounds have been synthesized and studied as s-PS catalyst [3–13]. Among those complexes, Cp*TiX 3 , (in- denyl)TiCl 3 , and (substituted indenyl)TiCl 3 derivatives are the most active catalysts. Studies on the mechanism involved in the polymerization of styrene have also been reported [14 – 18]. The chemical and physical properties of cyclopenta- dienyl titanium complexes can be varied over a wide range by modification of the substituents on the cy- clopentadienyl ring [19]. Thus, many research groups are involved in the design of ligands to tailor the catalytic activity and product properties. However, a limited range of cyclopentadienyl titanium complexes containing such ligands have been prepared and studied due to the absence of a generalized synthetic method for substituted cyclopentadiene. Recently, Takahashi et al. [20] reported the synthesis of 1,2,3-trisubstituted cyclopentadienes through the reaction of zirconacy- clopentene with acid chloride in the presence of a catalytic amount of copper chloride. Several years ago, we reported [21] the general method for preparation of 1,2,3-trisubstituted cyclopentadienyls and their use in the preparation of manganese tricarbonyl and zirco- nium dichloride derivatives. The method can be easily extended to synthesize 1,2,3-trisubstituted cyclopentadi- enyl titanium trichlorides. Herein we report the synthe- sis and characterization of 1,2,3-trisubstituted cyclopentadienyl titanium trichloride and their behavior in styrene polymerization. 1 *Corresponding author. Tel.: +82-2-8806662; fax: +82-2- 8891598; e-mail: ykchung@plaza.snu.ac.kr 2 *Corresponding author. Tel.: +82-031-2191844; e-mail: bunyeoul@madang.ajou.ac.kr 0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S0022-328X(01)00749-5