Crystal Structure of ClF₄⁺SbF₆^-, Normal Coordinate Analyses of ClF₄⁺, BrF₄⁺, IF₄⁺, SF₄, SeF₄, and TeF₄, and Simple Method for Calculating the Effects of Fluorine Bridging on the Structure and Vibrational Spectra of Ions in a Strongly Interacting Ionic Solid

Abstract

The crystal structure of the 1:1 adduct ClF(5).SbF(5) was determined and contains discrete ClF(4)(+) and SbF(6)(-) ions. The ClF(4)(+) cation has a pseudotrigonal bipyramidal structure with two longer and more ionic axial bonds and two shorter and more covalent equatorial bonds. The third equatorial position is occupied by a sterically active free valence electron pair of chlorine. The coordination about the chlorine atom is completed by two longer fluorine contacts in the equatorial plane, resulting in the formation of infinite zigzag chains of alternating ClF(4)(+) and cis-fluorine bridged SbF(6)(-) ions. Electronic structure calculations were carried out for the isoelectronic series ClF(4)(+), BrF(4)(+), IF(4)(+) and SF(4), SeF(4), TeF(4) at the B3LYP, MP2, and CCSD(T) levels of theory and used to revise the previous vibrational assignments and force fields. The discrepancies between the vibrational spectra observed for ClF(4)(+) in ClF(4)(+)SbF(6)(-) and those calculated for free ClF(4)(+) are largely due to the fluorine bridging that compresses the equatorial F-Cl-F bond angle and increases the barrier toward equatorial-axial fluorine exchange by the Berry mechanism. A computationally simple model, involving ClF(4)(+) and two fluorine-bridged HF molecules at a fixed distance as additional equatorial ligands, was used to simulate the bridging in the infinite chain structure and greatly improved the fit between observed and calculated spectra.

Phenyliodine(V) fluorides

“…The third fluorine atom (IÀF ¼ 182:1(3) pm) and the ipso carbon atom (IÀC ¼ 208:4(5) pm) occupy equatorial positions in the pseudo-trigonal-bipyramidal structure. The cations ClF 4 þ , BrF 4 þ , and IF 4 þ all have similar structures[29]. The two Sb-FÁ Á ÁI contacts to neighbouring SbF6 À units in C 6 H 5 IF 3 þ SbF 6 À complete the pseudo-pentagonal-bipyramidal structure with two axial fluorine atoms.…”

Heterocations in Superacid Systems

“…The bond angle and bond length for ICl 2 þ 334 were found to be 92. [835][836][837] All three salts contain discrete ions with the cation having pseudotrigonal bipyramidal structure like SF 4 with two fluorines occupying the axial positions and two fluorines and a lone pair occupying the equatorial positions (337 . The electrical conductivity of ICl 3 (specific conductance ¼ 9.85 10 À2 ohm À1 cm À1 ) can be attributed to the self-ionization.…”

“…5 . [837][838][839][840] Because of discrepancies between the observed and calculated values, Christe and co-workers 841 846,847 it is the only known example of a fluorocation derived from the hitherto unknown compounds (i.e., NF 5 and ClF 7 ). 828 I 2 Cl þ Ion.…”

The Solid‐State Structure of SF4: The Final Piece of the Puzzle

“…[2] The structure of SF 4 has been determined in the gas phase by microwave spectroscopy [3] and electron diffraction, [4] revealing its molecular seesaw geometry (C 2v ), which is in accord with the VSEPR model. [5] Sulfur tetrafluoride is one of the typical examples for a fluxional trigonal bipyramidal geometry, with rapidly exchanging axial and equatorial fluorine environments on the NMR timescale at room temperature. [5] Sulfur tetrafluoride is one of the typical examples for a fluxional trigonal bipyramidal geometry, with rapidly exchanging axial and equatorial fluorine environments on the NMR timescale at room temperature.…”

“…The effect of coordination of fluoride on the structure of SF 4 in this salt is however less pronounced than that of N(C 2 H 5 ) 3 coordination observed in the structure of SF 4 ·N(C 2 H 5 ) 3 , [13] reflecting the weaker interaction between SF 4 and a fluoride that is hydrogen-bonded to two cations. As mentioned for the anion in Rb ] cations and the F À and SF 5 À anions. The second fluoride ion in the structure is sufficiently naked to form the SF 5 À anion, which adopts the expected square pyramidal structure.…”