Hydrogen-Transfer Reactions Catalyzed by Low-Valent, Tertiary Phosphine Complexes of Zirconium. Molecular Structure of Hydrido(η5-cyclooctadienyl)biszirconium

Article abstract of DOI:10.1021/ja00535a019

Treatment of ZrCl4(dmpe)2 (dmpe = 1,2-bis(dimethylphosphino)ethane) with Na/Hg and 1,3-cyclohexadiene or 1,3-cyclooctadiene affords ZrH(η⁵-cyclohexadienyl)(dmpe)2 or ZrH(η⁵-cyclooctadienyl)(dmpe)2, respectively.The crystal structure of ZrH(η⁵-C8H11)(dmpe)2 was determined and refined to a conventional R factor of 0.066.Although there were several spurious peaks on the ΔF map in the neighborhood of Zr, a peak 1.67 Angstroem from it is assigned to the hydrogen (i.e., hydride) atom.Five carbon atoms of C8H11 are sp² hybridized, coplanar, and approximately the same distance (2.43-2.47 Angstroem) from Zr.ZrH(η⁵-C6H7)(dmpe)2 catalyzes the disproportionation of 1,3-cyclohexadiene to benzene and cyclohexene, as well as a number of related hydrogen-transfer reactions.