Hydrovinylation of olefins catalyzed by cationic nickel complexes [Ni(2,4,6-Me3C6H2)(CH3CN)P2]BF4

Article abstract of DOI:10.1016/S1381-1169(97)00082-4

The hydrovinylation of several olefins and alkynes by the ionic nickel precursor trans-[Ni(2,4,6-Me₃C₆H₂((CH₃CN((P(CH₂Ph)₃)₂]BF₄ in THF solution was studied. The activity of the catalytic system showed strong dependence on the nature of the substrate. Only conjugated diolefins and some strained mono-olefins led to hydrovinylation products with nearly complete conversion. Selectivity was also variable: for norbornene, exo-2-vinylnorbornane (94%) was obtained selectively, whereas isoprene gave a mixture of 9 hydrovinylation compounds. The turnover rate of the reaction at 25°C and 15 bar of initial pressure of ethylene with an olefin/[Ni] ratio of 1000/1 was 4300 h^-1 for norbornene and 30 h^-1 for isoprene. The chiral monodentate phosphines, (cis-myrtanyl)diphenylphosphine and myrtenyldiphenylphosphine, were obtained. The catalytic precursors containing these phosphines were being tested in the hydrovinylation of styrene and norbornene, and the enantiomeric excess obtained was between 3-7%. Diphenylacetylene was also found to be active in the hydrovinylation reaction; cis- and trans-3,4-dipbenyl-1,3-hexadiene, products of a double vinylation of the triple bond were obtained.