Reduction of 1-hexene with Cp3Ln-NaH (Cp = cyclopentadienyl, Ln = lanthanide group metal) at 45?affords, after hydrolysis, hexane. The reductive activities of Cp3Ln strongly depend upon the ionic radius of the trivalent rare earth ion. The decrease in activity of seven Cp3Ln is in agreement with the gradually decreasing radius of Ln3+, except for variable valency elements Sm3+ and Yb3+. Therefore the general activity decreases in the order: Cp3Sm > Cp3La > Cp3Pr > Cp3Nd > Cp3Tb > Cp3Y > Cp3Er > Cp3Lu > Cp3Yb. The reaction path was strongly affected by the molar ratio of Cp3Ln to 1-hexene. If the ratio of Cp3Ln/1-hexene > 1, reduction of 1-hexene occurred predominately. When the ratio of Cp3Ln/1-hexene was 0.05, isomerization of 1-hexene took place, generating 2-hexene in excellent yield with cis- and trans-isomers in a 1:1 ratio. Moreover, Cp3Ln-NaH system is also able to reduce regioselectively dienes which contain both a terminal olefin as well as an internal double bond. By using Cp3Sm-NaH as reducing agent, the regioselective reduction of 4-vinyl-1-cyclohexene affords 4-ethyl-1-cyclohexene in high yield. A probable mechanism is proposed for reduction of 1-hexene.

Key words: SODIUM COMPOUNDS, DIMER, REACTION MECHANISM, CYCLOPENTADIENE P, ALKENE, ORGANO TRANSITION METAL COMPOUNDS, YTTRIUM COMPLEX, HYDRIDES, RARE EARTH METAL COMPLEX, METALLOCENES