Yonggyu Han

Synthesis, structure and ethylene polymerization behavior of zirconium complexes with chelating ketoiminate ligands

Mixed ketoiminate/ketoimine/pentamethylcyclopentadienyl (Cp*) complex of zirconium, [(η5-Cp*){CH3C(O)CHC(NHR)CH3}{CH3C(O)CHC(NR)CH3}ZrCl2] (R=4-CF3Ph) (3) has been prepared in high yield by the reaction of one equivalent of 4-CF3-phenyl-β-ketoimine (1a) and one equivalent of lithium 4-CF3-phenyl-β-ketoiminate (2a) with one equivalent of Cp*ZrCl3 in Et2O. Bis(ketoiminate)zirconium dichloride complexes, 4 and 6, have been also prepared in high yield by the reaction of amine elimination of ketoimine ligands, respectively 1a and 1b, with Zr(NMe2)4 and followed by chlorination reaction with TMSCl. The X-ray crystallography reveals that the compound 3 is based on distorted octahedral geometry containing a ketoimine and a ketoiminate. The ketoiminate ligand coordinates to the zirconium as a bidentate ligand, leaving the metal center coordinatively unsaturated and thus leading to an additional binding of a ketoimine ligand to the metal to stabilize the complex 3. The zirconium complexes 3, 4 and 6 provide the moderate activity for the polymerization of ethylene in the presence of MMAO cocatalyst. Low molecular weight and high density polyethylene was obtained.

New half-sandwich metallocene catalysts for polyethylene and polystyrene

Abstract A new type of half-sandwich metallocene catalysts for the polymerization of ethylene and styrene, Cp*MCl(DEAR) (DEA=(OCH2CH2)2N, R=Me, M=Ti (1); R=Me, M=Zr (2); R=n-Bu, M=Ti (3)), was prepared by the reaction of corresponding N-alkyl-N,N-diethanolamine with Cp*MCl3 in the presence of triethylamine. Compounds 1–3 are slightly air-sensitive and thermally unstable. All catalyst systems show moderate activities in ethylene polymerization and especially the 2/MMAO system gives PE with broad molecular weight distribution at all polymerization temperatures. In addition, 1/MMAO and 3/MMAO show fairly good activities in sPS polymerization in the order 3/MMAO>1/MMAO.

New half-metallocene catalysts generating polyethylene with bimodal molecular weight distribution and syndiotactic polystyrene

A new type of half-metallocene catalyst for the polymerization of ethylene and styrene Cp * M((O) 3 O 9 Si 7 (c-C 5 H 9 ) 7 ) (M= Ti (1), Zr (2)) is prepared by the reaction of (HO) 3 O 9 Si 7 (c-C 5 H 9 ) 7 with Cp * MCl 3 in the presence of triethylamine. Complex 1 is stable to heat and air but heavier congener 2 is sligtly air sensitive. The catalytic systems 1/MMAO and 2/MMAO, in which MMAO is modified methylaluminoxane show good activities in ethylene polymerization, with that of 2/MMAO greater than that of 1/MMAO. Polyethylenes with bimodal molecular weight distributions were obtained. In addition, the catalytic system 1/MMAO shows fairly good activities for the syndiospecific polymerization of styrene.

Group 4 complexes derived from o-carborane: synthesis, structures and ethylene polymerization properties

Abstract Nine thermally stable complexes (η5-Cp*)[η5-(C5H4)CMe2CB10H10CR]MCl2 (R=H and Me) and (η5-Cp*)[η5; η1-(C5H4)CMe2(CB10H10C)]MCl have been prepared via metathesis reactions of Cp*MCl3 (M=Ti, Zr and Hf, Cp*=pentamethylcyclopentadienyl) with monolithium salts of (C5H5)CMe2(CB10H10CR) (R=H and Me) and with dilithium salt of (C5H5)CMe2(CB10H10CH), respectively. These compounds have been fully characterized by various spectroscopic methods and elemental analyses. All of the compounds except (η5-Cp*)[η5-(C5H4)CMe2CB10H10CMe]HfCl2 were additionally characterized by a single crystal X-ray diffraction study, establishing their monomeric bent metallocene structural feature with carborane acting as a substituent or an ancillary ligand. The titanium and zirconium complexes produce high-density polyethylenes with the activity range of about 103–104 g PE per mol of M bar h in the presence of modified methylaluminoxane cocatalyst.