Iron(II) Complexes with Redox-Active Tetrazene (RNNNNR) Ligands

This paper describes the redox chemistry of a tetrazene ligand on (β-diketiminato)iron complexes. Addition of 1-adamantyl azide to an iron(I) source gives the tetrazene complex LMeFe(AdNNNNAd), most likely through an imidoiron(III) intermediate. Spectroscopic, magnetic, crystallographic, and computational investigations of the tetrazene complex show that one unpaired spin occupies a primarily ligand-based orbital, and is antiferromagnetically coupled to a high-spin iron(II) ion to give an S = 3/2 ground state. Reversible single-electron reduction occurs at the ligand singly occupied molecular orbital (SOMO), affording a dianionic tetrazene ligand while leaving the metal oxidation state and spin state unchanged.