Multi-electron activation of dioxygen on zirconium(IV) to give an unprecedented bisperoxo complex

Although long proposed as key intermediates in different industrial and biological catalytic processes, bis(peroxides) of heavier transition metals have been elusive species for bulk manipulations. We report on the synthesis and structural characterization of the first such bisperoxo molecule of Zr(IV) as well as on its bis(diamido) precursor. Reduction of the glyoxal-bis(2,6-diisopropylphenyl) imine with magnesium powder in ether followed by reaction with ZrCl4 and extraction in hexane afforded the Zr(IV) bis(diamido) species 1. Further reaction with dry dioxygen produces the Zr(IV) bisperoxo compound 2, isolated as stable orange-brown crystals in 30% yield. X-ray diffraction data revealed an unprecedented quasi-orthogonal orientation of the two peroxide groups, which also have very long O-O bond distances of 1.512(4) and 1.504(4) angstrom.