Cis-2-Butene isomerization

There is an absence of cis-to-trans isomerization with conversion or time for the C8 (1,5-cyclooctadiene) polymer. This is shown from 52 to 58% conversion after 1 to 16 hours reaction time in Table II and III. The above review (A0, A2, A3, A5) shows that the cis structure in polymers from 1,5-cyclooctadiene using various chloride catalysts fell below 50% cis even to 20% cis units this means that the second cis double bond from the monomer underwent extensive cis-to-trans isomerization following the ring-opening of the first cis bond. Where cis-2-butene isomerizes to trans structure using other catalyst preparations, there is no evidence of this for cis-2-butene using the iodine system. However, polymer molecular... 

In most cases, complexes of primary alkyl ligands are more stable than the isomeric complexes of secondary or tertiary alkyl ligands. For example, Reger has shown that the secondary butyl iron complex in Equation 3.18 isomerizes to the corresponding primary n-butyl complex, and that the isopropyl palladium complex in Equation 3.19 isomerizes to the more stable -propyl isomer. Likewise, secondary zirconocene alkyl complexes isomerize to the linear isomers (Equation 320), as shown many years ago by Schwartz, and Labinger and Bercaw have recently shown that the sec-butyl complex of zirconocene, generated by the hydrozirconation of cis-2-butene, isomerizes in several hours to the corresponding n-butyl complex. ... 

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