Xe3OF3 +, a Precursor to a Noble-Gas Nitrate; Syntheses and Structural Characterizations of FXeONO2, XeF2·HNO3, and XeF2·N2O4

• Published in: Journal of the American Chemical Society Vol. 132; no. 39; pp. 13823 - 13839
• Main Authors: Moran, Matthew D., Brock, David S., Mercier, Hélène P. A., Schrobilgen, Gary J.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 06.10.2010
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja105618w

Xenon fluoride nitrate has been synthesized by reaction of NO2F with [FXeOXeFXeF][AsF6] at −50 °C. It was characterized in SO2ClF and CH3CN solutions by low-temperature 14N, 19F, and 129Xe NMR spectroscopy and in the solid state by low-temperature Raman spectroscopy (−160 °C) and single-crystal X-ray diffraction (−173 °C). The reactions were carried out using natural abundance and 18O-enriched [FXeOXeFXeF][AsF6] and 15NO2F to aid in the vibrational assignments of FXeONO2 and to establish the likely reaction pathway. Raman spectroscopy showed that FXe16ON(16O18O) was formed, along with XeF2 and [NO2][AsF6], when an excess of N16O2F reacted with [FXe18OXeFXeF][AsF6]. A reaction mechanism consistent with these findings is discussed. The crystal structure consists of well-separated FXeONO2 molecules which display no significant intermolecular interactions, providing geometric parameters that are in good agreement with the gas-phase values determined from quantum-chemical calculations. Decomposition of solid FXeONO2 is proposed to occur by three reaction pathways to give XeF2, Xe, O2, N2O5, N2O4, and NO2F. Attempts to synthesize FXeONO2 and Xe(ONO2)2 by reaction of XeF2 with HNO3 in SO2ClF solution below −30 °C led to XeF2·HNO3. The structure of XeF2·HNO3 includes a hydrogen bond between HNO3 and a fluorine atom of XeF2, as well as an interaction between the xenon atom and an oxygen atom of HNO3, leading to a crystal lattice comprised of layered sheets. A molecular addition compound between XeF2 and N2O4 crystallized from liquid N2O4 below 0 °C. The crystal structure of XeF2·N2O4 displayed weak interactions between the xenon atom of XeF2 and the oxygen atoms of N2O4. Quantum-chemical calculations have been used to assign the vibrational spectra of FXeONO2, XeF2·HNO3, and XeF2·N2O4 and to better understand the nature of the interactions of HNO3 and N2O4 with XeF2. The synthesis of [XeONO2][AsF6] was attempted by the reaction of FXeONO2 with excess liquid AsF5 between −78 and −50 °C, but resulted in slow formation of [NO2][AsF6], Xe, and O2. Thermodynamic calculations show that the pathways to [XeONO2][AsF6] formation and decomposition are exothermic and spontaneous under standard conditions and at −78 °C.