Synthesis, Characterization, and Polymerization Studies of Ethylenebis(hexamethylindenyl) Complexes of Zirconium and Hafnium

Abstract

The chemistry of a series of ansa-bridged ethylene-bis(hexamethylindenyl)zirconium and hafnium complexes has been explored. Treatment of EBI*Li 2 3 THF 0.38 with MCl 4 3 THF 2 (M = Zr, Hf) gives rac-EBI*MCl 2 (rac-2, rac-3) and meso-EBI*MCl 2 (meso-2, meso-3) (M=Zr and Hf), respectively. The rac-and meso-isomers can be separated by fractional crystallization. meso-EBI*ZrMe 2 (meso-4) can be prepared by alkylation of meso-2 with MeLi 3 LiBr. The molecular structures of racand meso-2 and racand meso-3 have been determined by single-crystal X-ray crystallography. A comprehensive structural comparison between these compounds and related ansa metallocenes has been carried out. racand meso-2 and racand meso-3 in the presence of modified methylaluminoxane (MMAO) are very active catalyst precursors for the polymerization of ethene to give high-density polyethene (HDPE) with molecular weights (M w ) in the range 100 000-220 000 and polydispersities (M w /M n ) of ca. 2.6. The activities of both catalyst precursors racand meso-2 are some of the highest reported in the literature, at 61 800 and 38 200 kg PE /mol met/h/bar, respectively.

Toward the Prediction of Activity in the Ethylene Polymerisation of ansa‐Bis(indenyl) Zirconocenes: Effect of the Stereochemistry and Hydrogenation of the Indenyl Moiety

“…In line with expectations, [17] complex rac-1 was more active than meso-1 (entry 1 versus entry 2 in Table 1). Unexpectedly, and in contrast to studies performed by Spaleck et al [18] hydrogenation of rac-1 provided a better pro-catalyst, namely, complex rac-2 (entry 1 versus entry 3 in Table 1).…”

Initiation of complex-radical polymerization of methyl methacrylate in the presence of metallocenes

“…A certain increase in the initial rate of polymerization is observed in the presence of Cp 2 TiCl 2 ( Table 2). The electrochemical potentials of Cp 2 TiCl 2 and (C 5 Me 5 ) 2 ZrCl 2 are unknown; for Cp 2 ZrCl 2 , the electrochemical potential is +1.86, i.e., far in excess of the values known for fer rocenes [17]. It is assumed that the potentials of Cp 2 TiCl 2 and (C 5 Me 5 ) 2 ZrCl 2 will likewise be above +1.…”

Synthesis and characterisation of permethylindenyl zirconium complexes and their use in ethylene polymerisation

“…The tilt angle, α ‡ , (58.50°), is slightly lower than that reported for either (SBI)ZrCl 2 (61.80°) or ( 2,4,6-Me 3 SBI)ZrCl 2 (59.18°). 26 The value of α is also in good agreement with that of rac-(EBI*)ZrCl 2 (57.15°), 7 This β ‡ value for rac-(SBI*)ZrCl 2 (18.89°), slightly exceeds those reported for ( 2,4,6-Me 3 SBI)ZrCl 2 (17.05°) or (SBI)ZrCl 2 (16.45°). 27 The average Zr- Illustrations of the DFT-computed (BP86) HOMO and LUMO are given in Fig.…”

“…However, the ethylene analogous compound demonstrated more than double this activity. 7 MAO-modified AMOST layered double hydroxides support led to higher activity with respect to silica supported pre-catalysts. rac-(EBI*)ZrCl 2 supported on the AMO-LDH Mg 2 Al-SO 4 , Mg 2 Al-CO 3 and Mg 2 Al-Cl displayed polymerisation activities of 4325 2719 and 2373 kg PE /mol Zr /h/bar respectively.…”

“…4,5 The electronic structure and spatial organisation of the active site of the catalyst, influenced by ligand structure, have profound effects on the microstructure of the polyethylene obtained and hence, the overall polymer properties. 6,7 Support materials provide a convenient way to serve as a template for the growing polymer particle. 8 Many materials have been tested as polymerisation supports including inorganic solids such as clays, 9 ZrO 2 , 10 SiO 2 , 11 and MgCl 2 .…”