Structure Elucidation of In Situ Generated Chiral Hypervalent Iodine Complexes via Vibrational Circular Dichroism (VCD)

• Published in: Angewandte Chemie International Edition 2022-12, Vol.61 (50), p.e202204624-n/a
• Main Authors: Golub, Tino P., Abazid, Ayham H., Nachtsheim, Boris J., Merten, Christian
• Format: Article
• Language: English
• Subjects: Asymmetric Catalysis; Catalysts; Circular Dichroism; Communication; Communications; Computational Chemistry; Dichroism; Hypervalent Iodine; Iodides; Iodine; Ligands; Mathematical analysis; Spectroscopy; Stereochemistry; Stereoisomerism; Substrates; Vibrational Spectroscopy
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202204624

The structure of in situ generated chiral aryl‐λ3‐iodanes obtained under oxidative reaction conditions was not yet observable with experimental techniques and their proposed structures are purely based on DFT calculations. Herein, we establish vibrational circular dichroism (VCD) spectroscopy as an experimental technique to verify DFT‐calculated chiral iodane structures. Based on a chiral triazole‐substituted iodoarene catalyst, we were able to elucidate a yet undescribed cationic chiral iodane as the most populated intermediate under oxidative conditions with a significant intramolecular N−I‐interaction and no significant interactions with tosylate or m‐chlorobenzoic acid as potential anionic ligands. Instead, aggregation of these substrates was found, which resulted in the formation of a non‐coordinating anionic hydrogen bonded complex. The importance of VCD as a crucial experimental observable is further highlighted by the fact that our initial structural proposal, that was purely based on DFT calculations, could be falsified. Due to their instability and reactivity, the structure of in situ generated iodane(III) species is challenging to characterize. VCD spectroscopy reveals a cationic species as the most important intermediate of a chiral triazole‐containing aryl‐λ3‐iodane catalyst under oxidative conditions.