On the Reactivity of F₃SNXeF⁺: Syntheses and Structural Characterizations of [F₄SN−Xe---NSF₃][AsF₆], a Rare Example of a N−Xe−N Linkage, and [F₃S(NSF₃)₂][AsF₆]

The F4SN−Xe---NSF3+ cation has been synthesized as the AsF6− salt by rearrangement of [F3SNXeF][AsF6] in NSF3 solvent at 0 °C. Deep yellow [F4SN−Xe---NSF3][AsF6], which crystallized from a NSF3 solution at −10 °C, was characterized by Raman spectroscopy (−160 °C) and by single-crystal X-ray diffraction (−173 °C). The Xe−N bond length (2.079(3) Å) of the F4SN−Xe---NSF3+ cation is among the shortest Xe−N bonds presently known. The F4SNXe+ cation interacts with NSF3 by means of a Xe---N donor-acceptor bond (2.583(3) Å) that is significantly longer than the primary Xe−N bond (2.079(3)Å) but significantly shorter than the sum of the Xe and N van der Waals radii (3.71 Å). The F4SN−Xe---NSF3+ cation undergoes a redox decomposition in NSF3 at 0 °C, forming [F3S(NSF3)2][AsF6], cis-N2F2, and Xe, which were characterized by low-temperature Raman spectroscopy in the solid state and by 19F NMR spectroscopy in NSF3 solvent (0 °C). Colorless [F3S(NSF3)2][AsF6] crystallized from NSF3 at −10 °C and was characterized by low-temperature, single-crystal X-ray diffraction. The S(IV) atom of F3S(NSF3)2+ has long contacts with the N atoms of two NSF3 molecules and a F ligand of a neighboring AsF6− anion. The arrangement of long contacts avoids, to the maximum extent, the F atoms of SF3+ and the nonbonding electron pair situated on the pseudo-3-fold axis opposite the F ligands of SF3+, providing distorted octahedral coordination about the S(IV) atom. Quantum-chemical calculations using MP2, B3LYP, and PBE1PBE methods were employed to arrive at the gas-phase geometries, charges, bond orders, valencies, and vibrational frequencies for F4SN−Xe---NSF3+ and F3S(NSF3)2+ to aid in the assignments of experimental vibrational frequencies. The F4SN−Xe---NSF3+ cation expands the known chemistry of the F4SN− group and is the first example of a N−Xe−N linkage to be structurally characterized by single-crystal X-ray diffraction.