Iodine Mössbauer Studies of Chemical Bonding in Iodobenzene and Several Polyvalent Iodine Derivatives

Mössbauer resonance experiments have been carried out at 4.2°K to investigate the iodine bonding in iodobenzene, iodobenzene dichloride, iodosobenzene, iodoxybenzene, and an iodosodilactone. The quadrupole splitting, asymmetry parameter, and isomer shift data have been analyzed to demonstrate the existence of pure $p$ bonding in all of the compounds except PhIO₂, where a small amount of $s$ hybridization in the iodine $p$ orbitals was found. A localized hybridization model cannot provide an adequate description of the iodine bonding in PhICl₂, PhIO, and the iodosodilactone, whereas a delocalized molecular orbital approach is in good agreement with the experimental results. The C–I–O bond angle in PhIO is shown to be near 90°, rather than linear, and the iodosodilactone has an approximately planar configuration with a linear IO₂ group. PhIO₂ has iodine orbital populations significantly different from the other compounds, which can be associated with an O–I–O bond angle of about 95° in this molecule.