A Cl nuclear quadrupole resonance study of NH4ICl4·H2O

The “missing” fourth ³⁵Cl NQR frequency postulated for NH₄ICl₄H₂O at room temperature has been observed. Four signals were also found for this compound at 195K, but the results at 77K were less clear-cut, with either five or (probably) six resonances detected. The occurrence of a phase transition between 77 and 195K seems likely. A structure is suggested for the ICl₄⁻ ion at room temperature from the relationship found previously between NQR frequency and bond length in tetrachloroiodates.