Synthesis and Characterization by 19F and 125Te NMR and Raman Spectroscopy of cis-ReO2(OTeF5)3 and cis-ReO2(OTeF5)4-, and X-ray Crystal Structure of [N(CH3)4+][cis-ReO2(OTeF 5)4-]

The pentafluorooxotellurate compound ReO2(OTeF5)3 has been synthesized from the reaction of ReO2F3 with B(OTeF5)3 and structurally characterized in solution by ¹⁹F and ¹²⁵Te NMR spectroscopy and in the solid state by Roman spectroscopy. The NMR and vibrational spectroscopic findings are consistent with a trigonal bipyramidal arrangement in which the oxygen atoms and an OTeF5 group occupy the equatorial plane. The ¹⁹F and ¹²⁵Te NMR spectra show that the axial and equatorial OTeF5 groups of ReO2(OTeF5)3 are fluxional and are consistent with intramolecular exchange by means of a pseudorotation. The Lewis acid behavior of ReO2(OTeF5)3 is demonstrated by reaction with OTeF5^-. The resulting cis-ReO2(OTeF5)4^- anion was characterized as the tetramethylammonium salt in solution by ¹⁹F and ¹²⁵Te NMR spectroscopy and in the solid state by Raman spectroscopy and X-ray crystallography. The compound crystallizes in the triclinic system, space group P1̄, with a = 13.175(7) Å, b = 13.811(5) Å, c = 15.38(1) Å, α = 72.36(5)°, β = 68.17(5)°, γ = 84.05(4)°, V = 2476(2) ų, Dcalc = 3.345 g cm^-3, Z = 4, R = 0.0547. The coordination sphere about Re^VII in cis-ReO2(OTeF5)4^- is a pseudooctahedron in which the Re-O double bond oxygens are cis to one another.