Nickel and Copper Complexes of Pyrrolecarboxamide Ligands – Stabilization of M 3+ Species and Isolation of Ni 3+ Complexes

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 NiIII and CuIII 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 MIII 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 MIII species. Notably, [ML]+ can also be obtained via O2 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..

Cobalt complexes of pyrrolecarboxamide ligands as catalysts in nitro reduction reactions: influence of electronic substituents on catalysis and mechanistic insights

Square-planar Co³⁺ complexes, displaying substrate binding abilities and facile Co^3+/2+ redox potentials, function as efficient catalysts for hydrazine-mediated reduction of aromatic, heterocyclic, as well as aliphatic nitro substrates.

Hydroxide-bridged dicopper complexes: the influence of secondary coordination sphere on structure and catecholase activity

This work illustrates the syntheses, structures and catecholase activities of dicopper(ii) complexes having a Cu(μ-OH)Cu core encased within a secondary coordination sphere intricately created by appended heterocyclic rings.

Pd(ii) complexes with amide-based macrocycles: syntheses, properties and applications in cross-coupling reactions

Square-planar Pd²⁺ complexes of macrocyclic ligands carrying electronic substituents are synthesized and characterized. These well-characterized complexes have been used in the Suzuki and Heck cross-coupling reactions.