Trilithium thio­arsenate octa­hydrate

The title compound, Li(3)AsS(4)·8H(2)O, is built up from infinite cationic [Li(3)(H(2)O)(8)](3+) chains which extend along [001] and are cross-linked by isolated tetra­hedral AsS(4) (3−) anions via O—H⋯S hydrogen bonds. Two Li and two As atoms lie on special positions with site symmetries -1 (1 × Li) and 2 (1 × Li and 2 × As). The [Li(3)(H(2)O)(8)](3+) chain contains four independent Li atoms of which two are in octa­hedral and two in tetra­hedral coordination by water O atoms. An outstanding feature of this chain is a linear group of three edge-sharing LiO(6) octa­hedra to both ends of which two LiO(4) tetra­hedra are attached by face-sharing. Such groups of composition Li(5)O(16) are linked into branched chains by means of a further LiO(4) tetra­hedron sharing vertices with four adjacent LiO(6) octa­hedra. The Li—O bonds range from 1.876 (5) to 2.054 (6) Å for the LiO(4) tetra­hedra and from 2.026 (5) to 2.319 (5) Å for the LiO(6) octa­hedra. The two independent AsS(4) (3−) anions have As—S bond lengths ranging from 2.1482 (6) to 2.1677 (6) Å [<As—S> = 2.161 (10) Å]. The eight independent water mol­ecules of the structure donate 16 relatively straight O—H⋯S hydrogen bonds to all S atoms of the AsS(4) tetra­hedra [<O⋯S> = 3.295 (92) Å]. Seven water mol­ecules are in distorted tetra­hedral coordination by two Li and two S; one water mol­ecule has a flat pyramidal coordination by one Li and two S. At variance with related compounds like Schlippe’s salt, Na(3)SbS(4)·9H(2)O, there are neither alkali–sulfur bonds nor O—H⋯O hydrogen bonds in the structure.