High-valent transition metal chemistry. Moessbauer and EPR studies of high-spin (S = 2) iron(IV) and intermediate-spin (S = 3/2) iron(III) complexes with a macrocyclic tetraamido-N ligand

Synthetic iron(IV) complexes are attracting interest both as models for putative intermediates of biochemical reactions as well as for proposed catalytic entities. We have previously reported the X-ray structure of [Et 4 N] [Fa IV -Cl(η 4 -MAC * )] (H 4 [MAC * ]= 1,4,8,11-tetraaza-13,13-diethyl-2,2,5,5,7,7,10,10-octamethyl-3,6,9,12,14-pantaoxocyclotetradecane), where iron is coordinated to a plane of four amide nitrogen anions of a macrocyclic ligand and to one axial chloride (Collins, T. J.; Kostka, K. L.; Munck, E.; Uffelman, E. J. Am. Chem. Soc. 1990, 112, 5637-5639)