On the reactivity of F(3)S[triple bond]NXeF(+): syntheses and structural characterizations of [F(4)S=N-Xe---N[triple bond]SF(3)][AsF(6)], a rare example of a N-Xe-N linkage, and [F(3)S(N[triple bond]SF(3))(2)][AsF(6)]

Abstract

The F(4)S=N-Xe---N[triple bond]SF(3)(+) cation has been synthesized as the AsF(6)(-) salt by rearrangement of [F(3)S[triple bond]NXeF][AsF(6)] in N[triple bond]SF(3) solvent at 0 degrees C. Deep yellow [F(4)S=N-Xe---N[triple bond]SF(3)][AsF(6)], which crystallized from a N[triple bond]SF(3) solution at -10 degrees C, was characterized by Raman spectroscopy (-160 degrees C) and by single-crystal X-ray diffraction (-173 degrees C). The Xe-N bond length (2.079(3) A) of the F(4)S=N-Xe---N[triple bond]SF(3)(+) cation is among the shortest Xe-N bonds presently known. The F(4)S=NXe(+) cation interacts with N[triple bond]SF(3) by means of a Xe---N donor-acceptor bond (2.583(3) A) that is significantly longer than the primary Xe-N bond (2.079(3)A) but significantly shorter than the sum of the Xe and N van der Waals radii (3.71 A). The F(4)S=N-Xe---N[triple bond]SF(3)(+) cation undergoes a redox decomposition in N[triple bond]SF(3) at 0 degrees C, forming [F(3)S(N[triple bond]SF(3))(2)][AsF(6)], cis-N(2)F(2), and Xe, which were characterized by low-temperature Raman spectroscopy in the solid state and by (19)F NMR spectroscopy in N[triple bond]SF(3) solvent (0 degrees C). Colorless [F(3)S(N[triple bond]SF(3))(2)][AsF(6)] crystallized from N[triple bond]SF(3) at -10 degrees C and was characterized by low-temperature, single-crystal X-ray diffraction. The S(IV) atom of F(3)S(N[triple bond]SF(3))(2)(+) has long contacts with the N atoms of two N[triple bond]SF(3) molecules and a F ligand of a neighboring AsF(6)(-) anion. The arrangement of long contacts avoids, to the maximum extent, the F atoms of SF(3)(+) and the nonbonding electron pair situated on the pseudo-3-fold axis opposite the F ligands of SF(3)(+), 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 F(4)S=N-Xe---N[triple bond]SF(3)(+) and F(3)S(N[triple bond]SF(3))(2)(+) to aid in the assignments of experimental vibrational frequencies. The F(4)S=N-Xe---N[triple bond]SF(3)(+) cation expands the known chemistry of the F(4)S=N- group and is the first example of a N-Xe-N linkage to be structurally characterized by single-crystal X-ray diffraction.