The [XeOXeOXe]2+ cation has been synthesized as its [µ-F(ReO2F3)2]– salt by reaction of ReO3F with XeF2 in anhydrous HF at –30 oC. Rapid decomposition to XeF2, ReO2F3, Xe, and O2 occurs when the solid or its HF solutions are warmed above –20 oC. The [XeOXeOXe]2+ cation provides an unprecedented example of a Xe(II) oxide and a noble-gas oxo-cation and rare example of a noble-gas dication. The crystal structure of [XeOXeOXe][µ-F(ReO2F3)2]2 consists of a planar, zigzag-shaped [XeOXeOXe]2+ cation (C2h) that is fluorine bridged through its terminal Xe atoms to two [µ-F(ReO2F3)2]– anions. Quantum-chemical calculations were used to aid in the vibrational assignments of [XeOXeOXe][µ-F(ReO2F3)2]2 and to assess the bonding in [XeOXeOXe]2+ by NBO, AIM, ELF, and MEPS analyses. Ion pair interactions occur through Re–Fμ---Xe bridges, which are predominantly electrostatic in nature and result from polarization of the Fμ-atom electron densities by the exposed core charges of the terminal xenon atoms. Each Xe(II) atom core is surrounded by a torus of xenon valence electron density comprised of the three valence electron lone pairs. The positive valence holes of the terminal Xe atoms and associated fluorine bridge bonds correspond to σ-holes and donor interactions similar to those encountered in “halogen bonding”. Acetonitrile and the potent oxidative fluorinator, XeF6, react at −40 oC in Freon-114 to form highly endothermic and shock-sensitive F6XeNCCH3 (1) and F6Xe(NCCH3)2.CH3CN (2). Their low-temperature X-ray structures show the adducted XeF6 molecules are among the most isolated XeF6 moieties thus far encountered in the solid state and provide the first examples of XeVI–N bonds. The geometry of the XeF6 moiety in (1) is nearly identical to the calculated and experimental distorted octahedral (C3v) geometry of gas-phase XeF6. The C2v geometry of the XeF6 moiety in (2) resembles the transition state proposed to account for the fluxionality of gas-phase XeF6. Energy-minimized, gas-phase geometries, vibrational frequencies, and Xe−N binding energies were calculated for (1) and F6Xe(NCCH3)2 (3). The Raman spectra of (1) and (2) were assigned by comparison with calculated vibrational frequencies and intensities. AIM, ELF and MEPS analyses show their Xe−N bonds are σ-hole type donor-acceptor bonds, where the N base VELP(s) of (1) and (3) coordinate into regions occupied by the Xe VELPs and oppose one another. This bonding modality appears to be unique.

[XeOXeOXe][µ-F(ReO2F3)2]2, F6XeNCCH3, and F6Xe(NCCH3)2: Syntheses, structures and bonding

251st National Meeting (2016)

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