Three oxidation states of the bis(3,5-di-tert-butyl-2-phenolato)azanido pincer ligand on chromium(III)

By Hollas, Aaron M.; Ziller, Joseph W.; Heyduk, Alan F.
Published in Polyhedron 2018

Abstract

Three monomeric complexes of chromium(III) containing the redox-active ligand derived from bis(3,5-di-tert-butyl-2-phenol)amine, [ONOcat]H3, were prepared and fully characterized. The potassium salt of [ONOq]1? reacted with CrCl3(THF)3 to afford [ONOq]CrCl2(THF) (1); whereas, the trilithium salt of [ONOcat]3? reacted with CrCl3(THF)3 in the presence of pyridine to afford [ONOcat]Cr(py)3 (3). The three electron series was completed by reacting 1 with K[bpy] to afford [ONOsq]CrCl(bpy) (2). All three members of the series were characterized by structural, spectroscopic, and electrochemical methods. Attempts to effect the two-electron reduction of 1 resulted in the formation of a bimetallic chromium complex, [ONOcat]Cr(py)22 (4), which was also structurally characterized. The reaction of 1 with aryl transfer reagents resulted in a mixture of one- and two-electron reactivity, comprising the expulsion of either phenyl radical or biphenyl from the chromium coordination sphere.

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