The solid-state 19F NMR spectrum of [N(CH3)4][IO2F2], a vibrational study of [N(CH3)4][IO3] and [N(CH3)4][IO3]·2H2O, and the X-ray crystal structures of [N(CH3)4][IO2F2] and [N(CH3)4][IO3]

The salts, [N(CH3)4][IO2F2] and [N(CH3)4][IO3], were characterized by single-crystal X-ray diffraction. Both salts crystallize in centrosymmetric space groups: [N(CH3)4][IO3], Pnma, a = 13.4330(8) Å, b = 7.0909(4) Å, c = 8.5035(5) Å, V = 809.98(8) Å3, Z = 4, and R = 0.0199 at −152 °C; [N(CH3)4][IO2F2], C2/m, a = 10.7047(5) Å, b = 14.6386(8) Å, c = 5.3082(3) Å, β = 92.561(3) V = 830.97(8) Å3, Z = 4, and R = 0.0260 at −152 °C. The 19F NMR spectrum of powdered, microcrystalline [N(CH3)4][IO2F2] showed broad lines that arise from residual dipolar coupling and result from the large quadrupole moment of the 127I nucleus. This represents the first example of quadrupolar effects from 127I manifested in the NMR spectrum of a spin-1/2 nuclide. The 19F lineshape was simulated using 1J(127I–19F) = −1000 Hz and a 127I quadrupolar coupling constant of 5000 MHz as preliminary values. Raman spectroscopic data are reported for the first time for [N(CH3)4][IO3] and [N(CH3)4][IO3]·2H2O. The prior conflicting vibrational assignments for the IO3− anion have been resolved and are supported by electronic structure calculations.

Fluorine in crystalline [N(CH3)4][IO2F2] gives rise to a broad signal in the solid-state 19F MAS NMR spectrum that exhibits residual dipolar coupling to the quadrupolar 127I nucleus. The crystal structure of [N(CH3)4][IO3] is reported, together with the vibrational spectra of [N(CH3)4][IO3] and [N(CH3)4][IO3]·2H2O. Figure optionsDownload as PowerPoint slide