A DFT overview of high-valent iron, cobalt and nickel tetraamidomacrocyclic ligand (TAML) complexes: The end of innocence?

Amidato-N ligands are normally viewed as classic, strongly σ-donating, innocent ligands. However, when coordinated to high-valent transition metal centers, tetraamidomacrocyclic ligands are often substantially noninnocent, i.e., exhibit radical character involving the amido π-systems. Even the so-called MAC∗ ligand, generally considered to be an innocent ligand, is noninnocent in several of its known complexes.