Cyclooctadienes isomerisation

Cyclooctadiene 1,5 is isomerised even under mild conditions to cyclooctadiene 1, 3. 

The conditions of reaction of cyclooctadiene with Pd(II) and Pt(II) are critical in determining whether the olefin isomerizes during complex formation. Thus complexes of 1,4- and 1,5-cyclooctadiene with both metals have been prepared without any apparent isomerization , whereas under different conditions phosphine complexes of Pd(II) and Pt(II) isomerise the nonconjugated cyclooctadienes to the 1,3 isomer. Similarly while 1,4-cyclooctadiene reacts with KjCPtClj in water to form Pt(l,4-COD)Cl2, it forms [Pt(l,5-COD)Cl2] in 50% aqueous ethariol . 

---