“Oxidative Addition” to a Zirconium(IV) Redox-Active Ligand Complex

A strategy to enable reactivity analogous to oxidative addition is
presented for d0 transition-metal complexes. The reaction of the
redox-active ligand 2,4-di-tert-butyl-6-tert-butylamidophenolate (ap)
with ZrCl4(THF)2 affords the new complex ZrIV(ap)2(THF)2. This
compound is formally zirconium(IV) and contains no d electrons;
however, exposure of ZrIV(ap)2(THF)2 to chlorine gas results in
swift chlorine addition at the zirconium metal center via one-electron
oxidation of each ap ligand. The diradical product, ZrIVCl2(isq)2
(isq = 2,4-di-tert-butyl-6-tert-butyliminosemiquinone), has been
characterized by X-ray crystallography, electron paramagnetic
resonance spectroscopy, and SQUID magnetometery.