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.

The mixed-ligand complexes [Ti 2 (µ-OR) 2 (OR) 2 (κ 3 -tbop) 2 ] (1a) for R = Me and (1b) R = Et were prepared by the reaction of Ti(OR) 4 and H 2 tbop {H 2 tbop = 2,2Ј-thiobis[4-(1,1,3,3-tetramethylbutyl)phenol]} in methanol. Treatment of 1a and 1b with AlMe 3 led to the substitution of terminal alkoxy groups to create the organometallic compounds [Ti 2 (µ-OR) 2 (κ 3 -tbop) 2 (Me) 2 ] (2a) for R = Me and (2b) for R = Et. Controlled hydrolysis of 2b causes the evolution of methane and the formation of the titanoxane compounds [{Ti 2 (µ-OEt) 2 (κ 3 -

Titanium complexes based on 2,2′‐thiobis[4‐(1,1,3,3‐tetramethylbutyl)phenolato] (tbop) are prepared by reaction of TiCl4 or Ti(NMe2)4 with the parent biphenol. Three new complexes are reported: [Ti2(μ‐tbop‐κ3O,S,O)(μ‐tbop‐κ2O,O)‐(tbop‐κ3O,S,O)Cl2] (1)·2 CH3CN, [Ti2(μ‐tbop‐κ3O,S,O)2Cl4] (2) and [Ti(tbop‐κ3O,S,O)2] (3). Substitution of the chlorides in 1 and 2 by 2,6‐diisopropylphenolato and imido (NtBu) ligands generates the new compounds [Ti2(μ‐tbop‐κ3O,S,O)2‐Cl2(dipp)2] (4)·Et2O and [Ti2(μ‐tbop‐κ3O,S,O)2(NtBu)2‐(NH2tBu)2] (5), respectively. Treatment of 5 with crude Me3‐SiCl, containing Me3SiOH, produces [Ti(tbop‐κ3O,S,O)Cl(OSiMe3)(NH2tBu)] (6). Reaction of 2 with an excess of NHiPr2 provides a mixture of compounds: ionic [NH2iPr2][Ti(tbop‐κ3O,S,O)Cl3] (7)·CH2Cl2 and molecular [Ti2(μ‐tbop‐κ3O,S,O)2‐Cl2(NiPr2)2] (8). The structures of 1–8 were confirmed by NMR spectroscopy; complexes 1, 5, 6 and 7 were further investigated by X‐ray crystallography. Compounds 1, 2, 4 and 5, when supported on MgCl2 and activated with alkylaluminiums, effectively polymerise ethene. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)