F5SN(H)Xe+; a Rare Example of Xenon Bonded to sp3-Hybridized Nitrogen; Synthesis and Structural Characterization of [F5SN(H)Xe][AsF6]

• Published in: Inorganic chemistry Vol. 47; no. 10; pp. 4173 - 4184
• Main Authors: Smith, Gregory L, Mercier, Hélène P. A, Schrobilgen, Gary J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 19.05.2008
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic702039f

The salt [F5SN(H)Xe][AsF6] has been synthesized by the reaction of [F5SNH3][AsF6] with XeF2 in anhydrous HF (aHF) and BrF5 solvents and by solvolysis of [F3SNXeF][AsF6] in aHF. Both F5SN(H)Xe+ and F5SNH3 + have been characterized by 129Xe, 19F, and 1H NMR spectroscopy in aHF (−20 °C) and BrF5 (supercooled to −70 °C). The yellow [F5SN(H)Xe][AsF6] salt was crystallized from aHF at −20 °C and characterized by Raman spectroscopy at −45 °C and by single-crystal X-ray diffraction at −173 °C. The Xe−N bond length (2.069(4) Å) of the F5SN(H)Xe+ cation is among the shortest Xe−N bonds presently known. The cation interacts with the AsF6 − anion by means of a Xe---F−As bridge in which the Xe---F distance (2.634(3) Å) is significantly less than the sum of the Xe and F van der Waals radii (3.63 Å) and the AsF6 − anion is significantly distorted from Oh symmetry. The 19F and 129Xe NMR spectra established that the [F5SN(H)Xe][AsF6] ion pair is dissociated in aHF and BrF5 solvents. The F5SN(H)Xe+ cation decomposes by HF solvolysis to F5SNH3 + and XeF2, followed by solvolysis of F5SNH3 + to SF6 and NH4 +. A minor decomposition channel leads to small quantities of F5SNF2. The colorless salt, [F5SNH3][AsF6], was synthesized by the HF solvolysis of F3SNAsF5 and was crystallized from aHF at −35 °C. The salt was characterized by Raman spectroscopy at −160 °C, and its unit cell parameters were determined by low-temperature X-ray diffraction. Electronic structure calculations using MP2 and DFT methods were used to calculate the gas-phase geometries, charges, bond orders, and valencies as well as the vibrational frequencies of F5SNH3 + and F5SN(H)Xe+ and to aid in the assignment of their experimental vibrational frequencies. In addition to F5TeN(H)Xe+, the F5SN(H)Xe+ cation provides the only other example of xenon bonded to an sp3-hybridized nitrogen center that has been synthesized and structurally characterized. These cations represent the strongest Xe−N bonds that are presently known.