Effects of transition metals on hydrogen transfer and exchange in catalytic oligomerization of butadiene

Abstract

Linear oligomerization of three deuterium isomers of butadiene (C 4H 6, C 4H 2D 4, C 4D 6) was effected by CO 2(CO) 8-AIEt 3 (I) and Co(C 3H 5) 3, and cyclo-oligomerization of C 4H 6 by Ni(CO) 4-AIEt 3 (II) and Ni(C 3H 5) 2. Isotopic isomers of 3-methyl-1,4,6-heptatriene(MHT) were obtained; NMR studies indicated that only 1,4-hydrogens of butadiene migrate to form MHT and participate in hydrogen exchange between monomers. The hydrogen exchange rate was significant under the influence of (I), but negligible in the case of (II) as shown by mass spectroscopy of the deuterated butadienes recovered. Effectiveness of a transition metal for the hydrogen exchange appears to be a major factor in determining the reaction path.