Studies on organolanthanide complexes: XVIII. The reduction and isomerization of olefins with tricylopentadienyllanthanides/sodium hydride

Abstract Reduction of 1-hexene with Cp 3 Ln/NaH (Cp = cyclopentadienyl, Ln = rare earth metals) in THF at 45°C, after hydrolysis, gives hexane. The reducing activity of Cp 3 Ln depends strongly upon the ionic radius of the trivalent rare earth ion. The activity and selectivity of early rare earths for 1-hexane reduction are higher than those of heavy rare earths. The Cp 3 Ln/NaH systems can be used to regioselectively reduce dienes which contain a terminal carboncarbon double bond as well as an internal one with high yield. Selectivity is 100%. Moreover, the Cp 3 Ln/NaH systems are able to catalyze the hydrogenation of olefins. When Cp 3 Ln/Nah is used as catalyst, 1-hexene was isomerized at 45°C to cis -2-hexene and to trans -2-hexene in excellent yields. In contrast to reducing activity, the catalytic activity of heavy rare earths in the isomerization reaction is higher than that of the early earths. Hence, Cp 3 Sm/NaH and Cp 3 Y/NaH are new reducing agents and catalysts for 1-hexene reduction and isomerization, respectively.