We report on the synthesis of mono(aryloxido)titanium(IV) complexes of general formula {Ti[O(o-R)Ar]X 3 }, with X = OiPr, ArO = 2-tert-butyl-4-methylphenoxy and R = CMe 3 (2a), CMe 2 Ph (2b) and CH 2 NMe 2 (2c). Attempts to reach pure mono(aryloxido) complexes when R = CH 2 NMe(CH 2 Ph) (2d) or CH 2 N(CH 2 Ph) 2 (2e) were unsuccessful. When R = CH 2 OMe, the analogous mononuclear complex was not obtained, and instead, a dinuclear complex [(2-tert-butyl-4-methyl-6-methoxymethylphenoxy) TiCl(OiPr)(µ 2 -OiPr) 2 TiCl-(OiPr) 2 ] (3) was formed. Complexes 2b and 3 were characterized by single-crystal X-ray diffraction. The former contains a tetrahedrally coordinated Ti IV centre, whereas in the latter the aryloxido ligand behaves as a chelating-bridging ligand between the two, chemically very different metal

New titanium complexes of general formula [(ArO)(n)Ti(Oi-Pr)((4-n))] were synthesized and used as pre-catalysts for the selective dimerization of ethylene to 1-butene. The complexes were prepared in cyclohexane using [Ti(Oi-Pr)(4)] and one or two equivalents of the corresponding phenols (ArOH) at room temperature. In this work, both monodentate and chelating phenols were evaluated. For alkyl-substituted phenols, it was demonstrated that large steric hindrance at both ortho and ortho' positions selectively yielded the mono-substituted complexes [(ArO)Ti(Oi-Pr)(3)]. Substitution at only one of the ortho positions allowed both the mono- and the di-substituted Ti complexes to be isolated. When a heteroatom was introduced on the phenol backbone, di-substitution systematically occurred except with phenols presenting a hemilabile -CH(2)NR(2) group at the ortho position. Upon activation with 3 equiv. of AlEt(3) at 20 bar and 60 °C, all the complexes selectively dimerized ethylene to 1-butene (>86% of butenes among which 99% of 1-butene). An increase of the steric bulk at the ortho position of the ligand or the introduction of a functional group led to decreased activity compared to [Ti(Oi-Pr)(4)].