Abstract: Catalytic isomerization of 1,5 hexadiene by Cp 2Ln Schiff base/NaH (Schiff base= C 14 H 14 NO 2, Ln=Sm, Dy, Y, and Er) systems was studied. The isomerization results in a mixture of 1,4 hexadiene, 2,4 hexadiene, 1,3 hexadiene, methylene cyclopentane and methylcyclopentene. The effects of nature of catalyst, temperature, amount of catalyst, and time on isomerization rate and product compositon were also studied. The ratio of linear to cyclic product in reaction depends upon the amount of catalyst used.