Structure of and electronic interactions in aromatic polyvalent iodine compounds: A ¹³ C NMR study

Available data on the structures, electronic substituent effects and ¹³ C NMR spectra of aromatic polyvalent iodine compounds, particularly iodoso and iodoxy derivatives, are summarized and discussed. A series of aromatic tri- and penta-valent iodine compounds were synthesized, their ¹³ C NMR spectra were measured and the substituent chemical shifts (SCS) for several polyvalent iodine functional groups were calculated. As the oxidation state of iodine increases (I → II → V), the strong shielding of the ipso-carbon atom by iodine in aryl iodides due to the 'heavy-atom effect' (30 ppm) decreases substantially, and this decrease is apparently general for stable hypervalent iodine compounds. Possible explanations are discussed and correlations between chemical shifts, structures and/or electronic effects are proposed.