O-H ... S Hydrogen Bond in Barium Thiosulphate Monohydrate

THERE is evidence that the sulphur atom is capable of participating in hydrogen bonding systems in solids 1–3 , and numerous diffraction studies suggest that a few different types of this hydrogen bond may exist. Most of these studies are concerned, however, only with interatomic distances and angles involving the donor and acceptor atoms, and the position of the hydrogen atom has been determined in only a small number of cases. The type of X—H … S bond which is best known is that with X=N, and it has been shown by neutron diffraction that such bonds are present in, for example, both room and low temperature forms of thiourea 4 . The crystallo-chemistry of solid H 2 S (ref. 5) led Hamilton and Ibers 3 to believe that the S—H … S bond also occurs. Finally, the crystal structures of magnesium thiosulphate hexahydrate 6 , barium thiosulphate monohydrate 7 and 4,4′dihydroxythiobenzophenone monohydrate 8 , for example, indicate that the O—H … S bond may also exist, but these compounds were studied by X-ray methods in which the position of the hydrogen atom could not be determined. Further evidence is required to confirm the existence of the O—H … S bond in solids.