Coordination chemistry with pyridine/pyrazine amide ligands. Some noteworthy results

► The development of coordination chemistry utilizing an extensive class of deprotonated pyridine/pyrazine-2-carboxamide and pyridine-2,6-dicarboxamide-based chelating ligands is discussed. ► Spin-state properties of Fe(III), oxidation level of metal-coordinated ligand, and high (≥3) oxidation states of Fe, Co, Ni, and Ru have been presented. ► Differential behavior of five-/six-membered chelate ring formed by cobalt-coordinated alkyl-thioether is highlighted. ► Effect of donor atom type and metal stereochemistry on metal-centered E1/2 values has been critically analyzed.