Iodosylbenzene polymeric structure

Iodosylbenzene 18 is a pale yellow, amorphous powder and essentially insoluble in all nonreactive media. X-Ray powder diffraction and EXAFS spectroscopy showed a zigzag polymeric structure of 18 with the two 1-0 distances (2.04 and 2.377 A) and the I-O-I bond angle (114°) (Fig. 4) [214]. A similar polymeric structure was determined for the imido analogue, (tosyliminoiodo)benzene PhINTs [214,215]. Polymeric iodosylbenzene is likely to be terminated by addition of water, i.e. HO(PhIO)nH [216]. 

Polymeric structure of o-sulfonyl iodosylbenzene 135 with tetracoordinated iodine of pseudo square planar geometry was obtained by the single crystal X-ray analysis (Fig. 5) [217]. The bright yellow A3-iodane 135 is soluble in chloroform because of the weaker intermolecular hypervalent interaction (I-OT, 2.665 A) compared to that of iodosylbenzene 18 [218]. 

Hiller and coworkers reported an NMR and LC-MS study on the structure and stability of l-iodosyl-4-methoxybenzene and 1-iodosyl-4-nitrobenzene in methanol solution [195]. Interestingly, LC-MS analyzes provided evidence that unlike the parent iodosylbenzene, which has a polymeric structure (Section 2.1.4), the 4-substituted iodosylarenes exist in the monomeric form. Both iodosylarenes are soluble in methanol and provide acceptable and NMR spectra however, gradual oxidation of the solvent was observed after several hours. Unlike iodosylbenzene, the two compounds did not react with methanol to give the dimethoxy derivative ArI(OMe)2 [195]. 

Figure 2.4 Zigzag polymeric structure of iodosylbenzene, (PhlO)n, according to EXAFS analysis [122].

Alkenes and alkynes can be oxidatively functionalized by electrophilic X -iodanes, such as iodosylbenzene, [bis(acyloxy)iodo]arenes and organoiodine(lll) derivatives of strong acids. Iodosylbenzene itself has a low reactivity to alkenes due to the polymeric structure. However, the relatively weak electrophilic reactivity of (PhlO) can be increased considerably in the presence of BF3-Et20 or other Lewis acids. This activation... 

Although iodosylbenzene has been known and widely used as a reagent for over 100 years, structural details are still limited due to its amorphous polymeric nature, insolublility and low stability. On the basis of spectroscopic studies, it was suggested that in the solid state iodosylbenzene exists as a zigzag polymeric. 

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