Zirconocene-olefin complexes Cp2Zr(H2C=CHR), prepared in benzene-THF at 0 degreesC, react with acid chlorides to provide homoallylic alcohols. The key is an equilibrium between the zirconocene-olefin complexes and the corresponding zirconocene allyl hydride complexes via allylic C-H bond cleavage of the coordinating alkenes. Furthermore, the zirconocene-olefin complexes are also available for the reaction with 1,4-diketone to afford anti-1,4-diols with excellent diastereoselectivity. Thus, Cp2Zr(H2C CHR) serves as a donor of both hydride and an allylic group. These reactions also proceed efficiently by using zirconocene-olefin complexes, derived from Cp2ZrCl2, Mg metal, and 1-alkenes.