High-Valent Ni and Cu Complexes of a Tetraanionic Bis(amidateanilido) Ligand.

High-valent metal species are often invoked as intermediates during enzymatic and synthetic catalytic cycles. Anionic donors are often required to stabilize such high-valent states by forming strong bonds with the Lewis acidic metal centers while decreasing their oxidation potentials. In this report, we discuss the synthesis of two high-valent metal complexes [ML] + in which the Ni III and Cu III centers are ligated by a new tetradentate, tetraanionic bis(amidateanilido) ligand. [ML] + , obtained via chemical oxidation of ML , exhibits UV-vis-NIR, EPR, and XANES spectra characteristic of square planar, high-valent M III species, suggesting the locus of oxidation for both [ML] + is predominantly metal-based. This is supported by theoretical analyses, which also support the observed visible transitions as ligand-to-metal charge transfer transitions characteristic of square planar, high-valent M III species. Notably, [ML] + can also be obtained via O 2 oxidation of ML due to its remarkably negative oxidation potentials ( CuL / [CuL] + : -1.16 V, NiL / [NiL] + : -1.01 V vs Fc/Fc + in MeCN). This demonstrates the exceptionally strong donating nature of the tetraanionic bis(amidateanilido) ligation and its ability to stabilize high-valent metal centers..