High valent transition metal corrole and corrolazine complexes. The question of noninnocent ligands

Abstract

To contribute to the fundamental picture of the electronic structure of high valent first row transition metal complexes, I have carried out a density functional study of two different macrocyclic ligand systems, corroles and corrolazines, with two different axial ligands, Ph and Cl and a number of different central ions, P(V), Cu(III), Mn(IV) and Fe(IV). DFT calculations on Fe(IV) and Mn(IV) corrole and corrolazine derivatives suggest that compared with the often noninnocent corrole ligands, corrolazines are electronically more innocent and stabilize “purer” high-valent states of transition metal ions. This study also contributes to the idea that (Cor)FeIVCl complexes are best regarded as intermediate spin (S=3/2) Fe(III) centers antiferromagnetically coupled to a corrole ð-type cation radical, making the corrole ligand noninnocent. The nature of this coupling seems to be an Fe(dz2)-corrole(b1) orbital interaction for (Cor)FeIVCl. For (Cor)FeIVPh, however, the situation seems to be different. Like in the Fe(IV) corrole µ-oxo dimers, the corrole ligand has less radical character. DFT(PW91/TZP) studies of (Cor)MPh (M = Fe, Mn, Co) suggests that also metal(dzx)-corrole(a2) orbital interactions may contribute to the ligand noninnocence in high valent metal corrole complexes. In other words, different high-valent metallocorroles may exhibit b1-type, a2-type or no radical character.