NMRof Hypervalent Iodine Compounds

Abstract

Nuclear magnetic resonance (NMR) spectroscopy has played a key role in the rise of modern high‐valent halogen chemistry, especially for gaining solution‐state information on the corresponding organic derivatives. This chapter is focused on those aspects of NMR that have somehow proven specific to this family of compounds, including instances of abnormal chemical shifts, the highly electron‐withdrawing nature of the iodane group, and the presence of highly ionic hypervalent bond. In addition, the essay includes aspects that have had a particular impact on the development of this area of chemistry. The chapter is divided into six sections, with Section I introducing some of the general aspects of the NMR spectroscopy of high‐valent organoiodine species, including the normal halogen dependence (NHD) explanation for certain chemical shift abnormalities, the general iodine oxidation state influence on 1 H and 13 C chemical shifts, and certain challenges of solution‐state measurements for this class of compounds. Section II presents a discussion on the difficulty of directly measuring the halogen chemical shifts due to the nucleus' high quadrupole moments, especially for 127 I. Sections III and IV contain a discussion of some of the most relevant 13 C and 19 F NMR studies, including the key contributions of these two techniques to the understanding of the physical organic chemistry aspects of high‐valent halogen derivatives. Section V is dedicated to the NMR characterization via the less‐common nuclei, specifically 11 B, 31 P, 29 Si, and 17 O NMR, and includes a discussion of the role played by 17 O NMR in establishing the dynamic nature of certain key high‐valent carboxylates. Finally, Section VI presents a series of selected studies in which NMR is used to shed light on the mechanism of processes involving high‐valent iodine reagents.

X‐Ray and NMR Structural Data of Ethynylbenziodoxolones (EBXs) Reagents and Their Analogues

“…To continue our structural analysis, we then turned our attention to NMR spectra. [34,35] In 1 H-NMR spectra, the signals of HÀ C(2) and HÀ C(5) were considered as a reference, as the protons in such positions are supposed to be more significantly affected by electron shielding effects induced by the substituents on the iodoarene core and are usually better resolved. For 13 C-NMR spectra, we focused on the ethynyl carbons C (10) and C (11) and on the aromatic C(1) surrounding the iodine atom.…”