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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)].

In the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquid ([BMI][NTf(2)]), [Co(NTf(2))(2)] is reduced under 5.5 MPa of H(2)-CO to [Co(2)(CO)(8)] prior to [HCo(CO)(4)], provided a pyridine ligand is present in the medium.