Thermochemistry of some mono-substituted iodine fluorides and a comparison of gas and solid phase structures

Abstract

The heat of formation of iodine trifluoride, obtained from an ab initio calculation of its heat of dismutation to mono- and penta-fluorides, was close to their average value. The mean bond dissociation energies of these iodine fluorides is almost invariant. The reduction couples between penta and trifluoro, or tri and mono-fluoro compounds, were employed to calculate formation heats of phenyl and trifluoromethyl iodine fluorides via similar isodesmic reactions. The substituted derivatives were stronger oxidants than the unsubstituted iodine fluorides as quantified by their redox couples. Similarly the corresponding chloro-fluorides were stronger oxidants than the iodo-fluorides. Heats of formation of other iodine fluoride derivatives can be obtained by additivity methods. Recent X-ray structures, when compared with calculated gas-phase structures, showed a lesser tilt of axial I-F bonds to the vertical in the solids probably due to intermolecular association. Rotational barriers around C-I bonds were small enough to permit almost free rotation at ambient temperatures.