Zirconium borohydride piperazine complex, an efficient, air and thermally stable reducing agent

A zirconium borohydride piperazine complex (Ppyz)Zr(BH4)2Cl2, obtained by the reaction of an ethereal solution of ZrCl4 and LiBH4 with piperazine is a stable, selective and efficient reducing agent. (Ppyz)Zr(BH4)2Cl2 reduces aldehydes, ketones, silylethers, α,β-unsaturated carbonyl compounds and esters. The reactions were performed in diethyl ether at room temperature or under reflux, and the yields of the corresponding alcohols were excellent. The selective reduction of aldehydes in the presence of ketones and complete regioselectivity in the reduction of α,β-unsaturated carbonyl groups were observed.