Synthesis and properties of [NR4]3[SbS4] (R = Me, Et, n-Pr, n-Bu) and the crystal structures of [N(n-Bu)4]3[SbS4]⋅6H2O and [N(n-Bu)4]3[Sb(S2O3)3]·2THF

Abstract

The tetra-alkylammonium tetrathioantimonate(V) salts, [NR4]3[SbS4] (R = Me, Et, n-Pr, n-Bu), have been prepared in basic solution from aqueous [NR4]OH, sulfur and Sb2S3, and characterised by microanalysis, IR, Raman, 1H and 121Sb NMR spectroscopy. The crystal structure of [N(n-Bu)4]3[SbS4]·6H2O shows the presence of the tetrahedral [SbS4]3− anion (disordered over two sites), and also connected through an H-bonding network with the lattice water molecules. The alkylammonium salts are soluble in water and, with the exception of [NMe4]3[SbS4], are also soluble in weakly polar organic solvents, including halocarbons and MeCN. Solubility increases with the R group Me < Et < n-Pr < n-Bu, making the [N(n-Bu)4)3[SbS4] a convenient reagent to explore coordination chemistry or materials applications for which water as the solvent is not suitable. [N(n-Bu)4]3[Sb(S2O3)3]·2THF, the first thiosulfate complex of a p-block element, was produced by slow decomposition of [N(n-Bu)4]3[SbS4] in THF solution in the presence of the [NH(n-Bu)3]Cl (as a source of H+), confirming the instability of the [SbS4]3− anion in acidic media, and the crystal structure of [N(n-Bu)4]3[Sb(S2O3)3]·2THF shows a trigonal antiprismatic coordination geometry with a S3O3 donor set at the antimony(III) centre in the anion.