Crystal structure and the infrared and Raman spectra of potassium nitridosulphonate hydrate, K3[N(SO3)2]·H2O

Abstract

The crystal structure of the title compound has been determined using three-dimensional X-ray diffraction data with 1 386 ‘observed’ reflections. Crystals are triclinic, space group P with Z= 2 in a cell of dimensions a= 7.972(2), b= 6.758(2), c= 8.125(2)Å, α= 91.02(2), β= 97.85(2), and γ= 103.33(2)°. The structure has been solved using direct methods and refined by full-matrix least squares to R 0.042. The N–S bond length [1.609(2)Å] is markedly smaller than those for K[NH₂SO₃][1.666(6)], K₂[NH(SO₃)₂][1.674(5)], K₃[N(SO₃)₃]·2H₂O [1.71(2)], and NH₃⁺ SO₃^–[1.76(2)Å]. This contraction is attributed to the participation of the two lone pairs of electrons on nitrogen in π bonding. The i.r. (50–4 000 cm^–1) and Raman spectra of K₃[N(SO₃)₂]·H₂O and its ¹⁵N and ²H derivatives at 77 K are reported and interpreted according to the crystal structure. To assist with the assignment, spectra of the anhydrous salt K₃[N(SO₃)₂] and of an aqueous solution of the soluble sodium salt have also been recorded. ν_sym(N–S) and ν_asym(N–S) have been assigned wavenumbers of 794 and 1 046 cm^–1 respectively, δ(NS₂) at 190 cm^–1. The SO₃ groups show their characteristic group frequencies. Infrared spectra of partially deuteriated samples confirm the presence of two types of hydrogen bond per water molecule.