Structural and Electrochemical Studies of Novel Bis(mu-methoxo)diiron complexes:Observation of Fe~(III)Fe~(IV) and Fe~(IV)Fe~(IV) States Resonating with Phenoxyl Radicals

摘要

Novel diiron complexes with an Fe_2(mu-OMe)_2 core were studied as models of the active site of nonheme iron-containing enzymes.X-ray crystal structures of the complexes showed the existence of two types of ligand folding-parallel and twisted-both of which have four virtually equivalent phenolato groups sticking out from the Fe_2O_2 rhombic plane.Cyclic voltammetry measurements revealed two or more distinct redox waves in a region of relatively high potential,in addition to known Fe~(II)/Fe~(III) redox waves in a region of lower potential.These new peaks were assigned to the high-valence state of iron atoms,that is,Fe~(III) Fe~(IV) and Fe~(IV)Fe~(IV),resonating with the phenoxyl radical(s).The split width of the redox waves ranged from 0.14 to 0.20 eV,which may be a measure of the electronic interaction of the pheno-late groups through the Fe_2(mu-OMe)_2 core.