Ligand dynamics and reactivity of a non-innocent homoleptic iron complex (N,N)2Fe stabilized by phen-type ligands

Abstract

We report in this work the spectroscopic and reactivity properties of a non-innocent paramagnetic iron complex (bcp•–)2FeII featuring formally a Fe0 center stabilized by two bathocuproine (bcp) ligands. The origin of the paramagnetic 1H NMR behavior is analyzed by means of DFT calculations, and shows that two electronic states of the complex contribute to its spectroscopic properties. The dynamics of the coordination sphere in (bcp•–)2FeII is governed by the duality between the two electronic descriptions (bcp•–)2FeII, and (bcp)2Fe0. The strong antiferromagnetic coupling between the reduced bcp scaffolds and the ferrous ion in (bcp•–)2FeII makes substitution of the bcp•– ligand difficult; however, the reduced (bcp)2Fe0 character allows substitution of bcp by π-accepting ligands, such as alkynes, which can be activated in catalytic cycloadditions with the assistance of main-group salts. (bcp•–)2FeII also shows reductive activity towards a variety of organic electrophiles, and preliminary results using this complex as a catalyst for the reductive coupling of heteroaryl chlorides are discussed.