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

Abstract

AbstractWe 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 [(N3N′)FeCN] (4) by two consecutive single electron transfer (SET) processes from FeII precursor [(N3N′)FeLi(THF)] (1) with cyanobenziodoxolone (CBX). The FeIV complex can also be prepared by reaction of [(N3N′)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 [(N3N′)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.