ADDITION VON VINYL- UND ALLYL-TITAN-BINDUNGEN AN ETHYLEN

Article abstract of DOI:10.1016/S0022-328X(00)99254-4

Reaction of Cp2TiCl (1) with the alkylmagnesium halides 2a-2d, 2g (alkyl = Me, Et, Pr, iso-Pr, hexyl) and ethylene give bis(η⁵-cyclopentadienyl)(η³-1-methylallyl)titanium (3).Mechanistic investigations indicate that hydrogen transfer from ethylene either to the initially formed Cp2alkytitanium or to Cp2ethyltitanium, formed by βH-elimination to Cp2titaniumhydride and addition to ethylene, leads to liberation of alkane or alkene and ethane and formation of Cp2vinyltitanium F as an intermediate.Insertion to ethylene (even below 0 deg C) into the vinyl-titanium bond of F leads to Cp23-butenyltitanium, which isomerizes to 3.Reaction of 3 at ca. 80 deg C with ethylene in toluene occurs in part with hydrogen transfer to give the butene isomers 4, 5 and F and in part with addition of the allyl-titanium bond to ethylene to give the 2,4-hexadiene isomers 6a-6c by βH-elimination.The compounds 6a-6c are also formed in the catalytic codimerization of butadiene with ethylene in the presence of 3.This reaction has a regioselectivity of above 99percent.