Heptafluorides, structures

Heptadecararbonylhexaosmium clusters, reactions with nucleophiles, 30 196 Heptafluorides, structures, 27 108 Heptafluoro-n-propyl phosphorus compounds, 3 378... 

The heptafluoride has been reported not to have a pentagonal bipyramidal arrangement in the solid state,49 although the considerable difficulties involved in the crystal structure determination lead to less accurate results than could be desired.50 In the vapour state electron diffraction results51 show that the pentagonal bipyramidal arrangement is present but the molecule is non-rigid, with deformation from D5h symmetry, and this may account for the solid state structure. 

The octafluoroiodate(VII) ion has been reported52 to result from the interaction of the heptafluoride with the fluoride donors CsF or NOF, but its structure has not been determined. 

IF6+ Ion. Iodine heptafluoride has been shown to form the adduct IF7AsF5 and IF7-3 SbF5.852 The latter complex was postulated to have the ionic structure IF43+(SbF6 )3. These findings were questioned by Christe and Sawodny,853 who indicated that the adduct may contain IF6+ cation. Indeed they showed that the IF7AsF5 adduct is... 

Only two transition metal heptafluorides are known. Rhenium hep-tafluoride is stable, but osmium heptafluoride is so unstable that no structural results for the solid compound have been reported (4). The rhenium compound is cubic (92) at room temperature, with unit-cell dimension a = 6.26(2) A, which is the same as that for rhenium hexafluoride (Table V). This cubic form is stable to -90°C, when a transition occurs to a form of lower symmetry, for which unit-cell dimensions are unknown (92). 

Iodine heptafluoride, IF7, has a pentagonal bipyramidal structure of at least approximately D5h symmetry [118], Its dynamic behavior has been desribed by pseudorotation. The rearrangement that characterizes the PF5 molecule also describes well the permutation of... 

The heptafluoride OsF7 is made by fluorination of the metal at 600 °C under a fluorine pressure of 400 atm. The IR spectra suggest that the complex has a pentagonal bipyramidal (DSh) structure. The magnetic susceptibility was measured from 90 to 195 K. and, as with [OsF6]2 salts, the moment is essentially invariant with temperature over this range = 1.08 BM).788... 

Recent evidence favors Dg symmetry and a pentagonal bipyramidal structure for the heptafluoride. Claassen et al. (2) review the earlier debate about structure of lower symmetry. They provide convincing evidence of D symmetry from the first observation of Raman spectra of the vapor state and re-examination of the infrared spectra. Their data—including five fundamentals in Raman (two polarized), five fundamentals in infrared, no coincidences between Raman and infrared, and one fundamental inactive—are consistent only with symmetry. This is confirmed by Falconer et al. (4) who interpret their electric-deflection experiments as indicating a symmetry-forbidden dipole moment. Extended Huckel-molecular-orbital calculations (5) also predict Dg symmetry. The adopted structural parameters are from our approximate analysis of the electron-diffraction data of Thompson and Bartell (6). The authors gave a radial distribution curve and suggested only a gross (unrefined) structure because of the probable presence of... 

The number of species isoeiectronic with XeF, is quite limited. The anions SbBr, TeCl , and TeBr are octahedral. Both IF and XeF are nonoctahedral." Iodine heptafluoride and rhenium heptafluoride may be considered isoeiectronic with these species if they are all considered to have 14 valence shell electrons of approximately equal steric requirements. Both have a pentagonal bipyramidal structure (see Fig. 6.12). Most interestingly, the XeF anion, formed by the Lewis acid XeF ... 

Iodine Heptalluoride. Iodine heptafluoride (IF7) is the only known heptafluoride. Its structure is pentagonal bipyramidal (5). It is a stronger fluorinating agent than IF5 and reacts with H2O to give the oxyfluoride IOF5 and HF. The oxyfluorides will be discussed in the following section as a separate class of compounds. 

Vogt T, Fitch AN, Cockcroft JK (1994) Crystal and molecular structures of rhenium heptafluoride. Science 263 1265-1267... 

The molecular structures of some representive neutral interhalogens, (a) chlorine trifluoride, CIF3 (distorted T-shaped) b) bromine pentafluoride, BrFs (square pyramidal) (c) iodine heptafluoride, IF7 (pentagonal bipyramidal) and (d) diiodine hexachloride, I2CI6 (planar dimer). 

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