XeOF₃⁻, an Example of an AX₃YE₂ Valence Shell Electron Pair Repulsion Arrangement; Syntheses and Structural Characterizations of [M][XeOF₃] (M = Cs, N(CH₃)₄)

Abstract

The XeOF(3)(-) anion has been synthesized as its Cs(+) and N(CH(3))(4)(+) salts and structurally characterized in the solid state by low-temperature Raman spectroscopy and quantum-chemical calculations. Vibrational frequency assignments for [Cs][XeOF(3)] and [N(CH(3))(4)][XeOF(3)] were aided by (18)O enrichment. The calculated anion geometry is based on a square planar AX(3)YE(2) valence-shell electron-pair repulsion arrangement with the longest Xe-F bond trans to the oxygen atom. The F-Xe-F angle is bent away from the oxygen atom to accommodate the greater spatial requirement of the oxygen double bond domain. The experimental vibrational frequencies and trends in their isotopic shifts are reproduced by the calculated gas-phase frequencies at several levels of theory. The XeOF(3)(-) anion of the Cs(+) salt is fluorine-bridged in the solid state, whereas the anion of the N(CH(3))(4)(+) salt has been shown to best approximate the gas-phase anion. Although [Cs][XeOF(3)] and [N(CH(3))(4)][XeOF(3)] are shock-sensitive explosives, the decomposition pathways for the anions have been inferred from their decomposition products at 20 degrees C. The latter consist of XeF(2), [Cs][XeO(2)F(3)], and [N(CH(3))(4)][F]. Enthalpies and Gibbs free energies of reaction obtained from Born-Fajans-Haber thermochemical cycles support the proposed decomposition pathways and show that both disproportionation to XeF(2), [Cs][XeO(2)F(3)], and CsF and reduction to XeF(2), CsF, and O(2) are favorable for [Cs][XeOF(3)], while only reduction to XeF(2) accompanied by [N(CH(3))(4)][F] and O(2) formation are favorable for [N(CH(3))(4)][XeOF(3)]. In all cases, the decomposition pathways are dominated by the lattice enthalpies of the products.

[H(OXeF2)n][AsF6] and [FXeII(OXeIVF2)n][AsF6] (n = 1, 2): Examples of Xenon(IV) Hydroxide Fluoride and Oxide Fluoride Cations and the Crystal Structures of [F3Xe---FH][Sb2F11] and [H5F4][SbF6]·2[F3Xe---FH][Sb2F11]

“…Both starting geometries optimized to F 3 Xe---FH + (Xe---F, 2.537−2.556 Å), indicating that this is a better description than F 3 XeF---H + . This is supported by the similarities between the experimental and calculated geometrical parameters of XeF 4 The O 1 − IV Xe 1 −F bond angles are also greater than the F ax − IV Xe−F eq bond angles of XeF 3 + (83.3−84.2°; IV Xe−F eq NBO bond order, 0.50) as a result of the larger IV Xe 1 −O 1 bond domain.…”

“…In contrast with the IV Xe 1 −O 1 bond length trends, the IV Xe 1 −F bond lengths follow the reverse order and are shorter in the cations (FXeOXeF 2 + , 1.921−1.946 Å; HOXeF 2 + , 1.903− 1.927 Å; [HOXeF 2 ][AsF 6 ], 1.938−1.963 Å) than in XeOF 2 (1.968−1.997 Å), 4 but are longer than the related Xe−F ax bonds of XeF 3 + (1.883−1.906 Å) (Table S2, Supporting Information).…”

Gas-Phase Ion Chemistry of the Noble Gases: Recent Advances and Future Perspectives

“…This species is, however, definitely less stable and structurally less compact than the xenon covalent anions observed in the condensed phase. 14,[205][206][207][208][209] The pentacoordinated XeF 5 -, in particular, is a covalent species of D 5h symmetry, with short Xe-F distances of 2.012 Å. 205 Consistently, the Faffinity of XeF 4 is theoretically estimated to be as large as 247.3 kJ mol -1 .…”

Anorganische Chemie 2010

“…Die Verbindungen sind nur bei tiefen Temperaturen stabil und ausgesprochen schockempfindlich. Die Zersetzung der Salze ist dabei abhängig von den Kationen und wird im Wesentlichen durch die Gitterenthalpien der Zersetzungsprodukte bestimmt 1_66…”