homogeneous and heterogeneous oligomerization reactions of olefins with unbridged metallocene catalysts

1-pentene and 1-hexene were respectively reacted with 13 homogeneous metallocene catalysts to give linear oligomerization products, predominantly dimers, with selectivities above 90%. the product distributions of the codimerization reactions of 1-pentene with 1-hexene reflected a binomial behavior. therefore, the ratio for dimers is 1:2:1 (c10:c11:c12) while the trimers (pentadecenes up to octadecenes) show a proportion of 1:3:3:1. by changing the ratio of the 1-pentene/1-hexene mixture, the binomial distribution switched to the side of products of the higher concentrated monomer. even when using methyl branched olefins, the binomial product distribution could be observed. alkenes with an internal double bond could not be dimerized under these conditions. the reactions with olefins containing a methyl group in β-position, a tert-butyl group or a neopentyl group failed. addition of appropriate additives like tributylphosphine or aluminum powder raised both the activities and the selectivities for dimers, which means that the fraction of undecenes obtained from the codimerization reactions of 1-pentene and 1-hexene increased.