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

• Published in: Angewandte Chemie International Edition 2022-05, Vol.61 (22), p.e202201699-n/a
• Main Authors: Souilah, Charafa, Jannuzzi, Sergio A. V., Demirbas, Derya, Ivlev, Sergei, Swart, Marcel, DeBeer, Serena, Casitas, Alicia
• Format: Article
• Language: English
• Subjects: Computer applications; Crystal structure; Cyanides; Electron transfer; Electronic structure; Group-Transfer Reactions; Hypervalent Compounds; Iodine; Iron; Iron(IV) Cyanide; Oxidants; Oxidation; Oxidizing agents; Reagents; Single crystals; Single electrons; Single-Electron Transfer; Spectroscopy; Structural analysis; Synthesis; Thermal instability
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202201699

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 [(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. Cyano λ3‐iodanes react with iron(II) and iron(III) complexes as cyano‐transfer one‐electron oxidants. This approach enables the straightforward synthesis of iron(III) and iron(IV) cyanide complexes, which have been thoroughly characterized by spectroscopic methods, including X‐ray diffraction, EPR, Mössbauer and NMR spectroscopies and computational methods.