Crystal structure, and the infrared and Raman spectra, of tripotassium methanetrisulphonate hydrate, K3[CH(SO3)3]·H2O

Abstract

The crystal structure of the title compound has been determined using three-dimensional X-ray diffraction data, from 839 reflections; crystals are orthorhombic, space group P2₁2₁2₁, with unit-cell dimensions a= 9.405(1), b= 9.405(1), c= 12.321(1)Å, Z= 4. The structure has been solved using direct methods and refined by fullmatrix least squares to R 0.045. The S–C–S angles (ca. 113°) indicate an expansion from tetrahedral stereochemistry and the S–C bond lengths (ca. 1.81 Å) are appreciably longer than those for K₂[CH₂(SO₃)₂](1.77 Å) and Ca[CH₃SO₃]₂(1.75 Å). The i.r. (4 000–50 cm^–1) and Raman spectra of K₃[CH(SO₃)₃]·H₂O and K₃[CD(SO₃)₃]·D₂O at 77 K are reported and interpreted according to the crystal structure. To assist with the assignment, spectra of the anhydrous salt, K₃[CH(SO₃)₃], and of aqueous solutions of the soluble lithium salts, have also been recorded. The SO₃ groups show their characteristic group frequencies: ν_sym(C–S) and ν_asym(C–S) are assigned to 762 and 820 cm^–1, respectively; δ_sym(CS₃) and δ_asym(CS₃) to 170 and ca. 210 cm^–1, respectively. I.r. spectra of samples containing the isotopically dilute HDO species confirm the presence of two types of hydrogen bond per water molecule.