Synthesis of FeIII and FeIV Cyanide Complexes Using Hypervalent Iodine Reagents as Cyano-Transfer One-Electron Oxidants.

We disclose a new reactivity mode for electrophilic cyano λ3 -iodanes as group transfer one-electron oxidants to synthesize FeIII and FeIV cyanide complexes. The inherent thermal instability of high-valent FeIV compounds without π-donor ligands (such as oxido (O2- ), imido (RN2- ) or nitrido (N3- )) makes their isolation and structural characterization a very challenging task. We report the synthesis of an FeIV cyanide complex [(N3 N')FeCN] (4) by two consecutive single electron transfer (SET) processes from FeII precursor [(N3 N')FeLi(THF)] (1) with cyanobenziodoxolone (CBX). The FeIV complex can also be prepared by reaction of [(N3 N')FeIII ] (3) with CBX. In contrast, the oxidation of FeII with 1-cyano-3,3-dimethyl-3-(1H)-1,2-benziodoxole (CDBX) enables the preparation of FeIII cyanide complex [(N3 N')FeIII (CN)(Li)(THF)3 ] (2-LiTHF ). Complexes 4 and 2-LiTHF have been structurally characterized by single crystal X-ray diffraction and their electronic structure has been examined by Mössbauer, EPR spectroscopy, and computational analyses.