BISBUTADIENETITANIUM(0) OLEFIN DIMERIZATIONS CATALYZED BY TITANIUM AND ZIRCONIUM BUTADIENE COMPLEXES

Article abstract of DOI:10.1016/S0022-328X(00)83048-X

The complex Ti(η-C4H6)2 (dmpe) (dmpe = 1,2-bis(dimethylphosphino)ethane) was prepared by Na/Hg reduction of TiCl4 (dmpe) in the presence of butadiene.The compound is a poorer Lewis base than is Zr(η-C4H6)2(dmpe), as it fails to form seven-coordinate adducts analogously to the Zr complex.Both complexes catalyze the dimerization of ethylene to 1-butene and, by cross dimerization with additional ethylene, 3-methyl-1-pentene and 2-ethyl-1-butene.Propene is converted to 2,3-dimethyl-1-butene. cis-2-Butene is very slowly dimerized to 3,4-dimethyl-1-hexene.On the basis of the products formed and their distribution, a mechanism involving formation of a metallocyclopentane complex is proposed.The reaction is first-order in olefin and is slowed by increasing substitution.Formation of a mono(olefin) complex is the probable rate-determining step.