Krzysztof Szczegot

Syntheses, structure, and reactivity of chiral titanium compounds: procatalysts for olefin polymerization.

Titanium complexes with chelating alkoxo ligands have been synthesised with the aim to investigate titanium active centres in catalytic ethylene polymerisation. The titanium complexes cis-[TiCl2(eta2-maltolato)2] (1, 89%), and cis-[TiCl2(eta2-guaiacolato)2] (2, 80%) were prepared by direct reaction of TiCl4 with maltol and guaiacol in toluene. The addition of maltol to [Ti(OiPr)4] in THF results in the formation of species [Ti(OiPr)2(maltolato)2] (3, 82%). The titanium compound cis-[Ti(OEt)2(eta2-maltolato)2] (4, 74%) was obtained by the transesterification reaction of species 3 with CH3CO2Et. When compound 4 is dissolved in THF a dinuclear species [Ti2(mu-OEt)2(OEt)4-(eta2-maltolato)2] (5, 45%) is formed. Reaction of [Ti(OiPr)4] with crude guaiacol in THF yields a solid, which after recrystallisation from acetonitrile gives [Ti4(mu-O)4(eta2-guaiacolato)] x 4CH3CN (6, 55%). In contrast, reaction of TiCl4 with crude guaiacol in tetrahydrofuran affords [Ti2(mu-O)Cl2(eta2-guaiacolato)4] (7, 82%). Crystallographic and electrochemical analyses of these complexes demonstrate that maltolato and guaiacolato ligands can be used as a valuable alternative for the cyclopentadienyl ring. These complexes have been shown to be active catalysts upon combination with the appropriate activator.

New intermediates for the synthesis of olefin polymerization catalysts: the complexes [M2(µ-Cl)2Cl4(thf)4](M = Ti or V, thf = tetrahydrofuran); crystal structures and properties

The dimeric titanium(III) and vanadium(III) complexes [M2(µ-Cl)2Cl4(thf)4](M = Ti 1 or V 2, thf = tetrahydrofuran) have been prepared by recrystallization of [MCl3(thf)3] from dichloromethane. In the dimers, composed of slightly distorted edge-sharing octahedra, the metal atoms separated by Ti ⋯ Ti and V ⋯ V distances of 3.711 (3) and 3.619(1)A, respectively, are surrounded by two terminal Cl atoms, two oxygen atoms of thf molecules and are linked by two bridging Cl atoms. The geometry around the titanium atoms differs from that around vanadium because the thf molecules and the terminal chlorine atoms are differently located with respect to the bridging chlorine atoms of the M2(µ-Cl)2 unit. High catalytic activity was found for ethylene polymerization by 1.

Synthesis and characterization of new di- and tetra-meric vanadium intermediates of olefin polymerization catalysts. Crystal structures of [V2(µ-Cl)2Cl4(MeCo2Et)4] and [{VOCl2[CH2(CO2Et)2]}4]·2CH2Cl2

The direct reaction of VCl3 and ethyl acetate yields [V2(µ-Cl)2Cl4(MeCO2Et)4]1. The compound [V2(µ-Cl)2Cl4{CH2(CO2Et)2}2]2 was obtained in dichloromethane via the substitution of MeCO2Et in 1 by ethyl malonate. During crystallization of 2, under the influence of dioxygen and moisture, the tetrameric compound [{VOCl2[CH2(CO2Et)2]}4]·2CH2Cl23 was formed. The crystal structures of 1 and 3 have been determined by single-crystal X-ray diffraction studies. The dimeric compound 1 exhibits six-co-ordinate VIII centres [separated by a V ⋯ V distance of 3.590(1)A] surrounded by two terminal Cl atoms, two carbonyl oxygen atoms of co-ordinated ethyl acetate molecules and linked by two bridging Cl atoms. In the tetrameric species 3, the four vanadium(IV) atoms have equivalent octahedral geometries, being bonded by two mutually cis chlorine atoms, two mutually cis oxygen atoms. High catalytic activity was found for 1, 2 and [V2(µ-Cl)2Cl4(thf)4](thf = tetrahydrofuran).

New 2-tetrahydrofurfuryloxotitanium(IV) intermediates for the synthesisof olefin polymerization catalysts

The complexes [TiCl 3 (tmen){η 1 -OCH 2 CH(CH 2 ) 3 O}] 1, [Ti 2 (µ-Cl) 2 Cl 4 {η 2 -OCH 2 CH(CH 2 ) 3 O} 2 ] 2 and [TiCl 4 (tmen)] 3 (tmen = Me 2 NCH 2 CH 2 NMe 2 ) have been synthesized and structurally characterized by X-ray diffraction. The crystals of 1 consist of monomeric [TiCl 3 (tmen){η 1 -OCH 2 CH(CH 2 ) 3 O}] molecules. Three chloride, one oxygen and two nitrogen atoms form a distorted octahedron around the titanium atom. Compound 2 has a dimeric structure. Each titanium atom is surrounded by two bridging chloride atoms, two terminal chloride atoms and two oxygen atoms of the 2-tetrahydrofurfuryloxide ligand. The crystals of compound 3 consist of monomeric molecules in which four terminal chloride atoms and two nitrogen atoms from the chelate tmen ligand form a distorted octahedron around Ti. High catalytic activity was found for 1 and 2.