A binuclear alkenyl-bridged zirconium complex catalyzes the chemoselective hydrogenation of 1,3-cyclooctadiene to cyclooctene

Abstract

The oligomeric hydrido zirconium complex [Cp2Zr(H)(CH2PPh2)]n (1) reacts with (η4-butadiene)zirconocene to yield the (μ-1-η1:1,2-η2-butenyl), (μ-phosphinomethylene) doubly bridged binuclear zirconocene complex [Cp2-Zr(μ-CHCHC2H5)(μ-CH2PPh2)ZrCp2] 2. Complex 1 reacts with butadiene to give 2 and Ph2PCH3. At 80°C complex 2 catalyzes the chemoselective hydrogenation of 1,3-cyclooctadiene to cyclooctene. Formation of a binuclear μ-alkenyl zirconium(IV)/zirconium(II) intermediate, similar to 2, is proposed to explain the effective protection of the remaininig CC double bond in the catalytic cycle. © 1990.