title: New bis(aryloxy)-Ti(IV) complexes and their use for the selective dimerization of ethylene to 1-butene.
abstract: 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)].
authors: IFPEnergies nouvelles Lyon, Rond point de l'échangeur de Solaize, Solaize, France.
authors: Fabien
authors: F
authors: Grasset
authors: Jean-Benoît
authors: JB
authors: Cazaux
authors: Lionel
authors: L
authors: Magna
authors: Pierre
authors: P
authors: Braunstein
authors: Hélène
authors: H
authors: Oliver-Bourbigou