| Abstract: | The monoclinic crystal structure of Na2SO3(H2O)7 is characterized by an alternating stacking of (100) cationic sodium–water layers and anionic sulfite layers along 100]. The cationic layers are made up from two types of Na(H2O)6] octahedra that form linear 1∞Na(H2O)4/2(H2O)2/1] chains linked by dimeric Na(H2O)2/2(H2O)4/1]2 units on both sides of the chains. The isolated trigonal–pyramidal sulfite anions are connected to the cationic layers through an intricate network of O—H…O hydrogen bonds, together with a remarkable O—H…S hydrogen bond, with an O…S donor–acceptor distance of 3.2582 (6) Å, which is about 0.05 Å shorter than the average for O—H…S hydrogen bonds in thiosalt hydrates and organic sulfur compounds of the type Y—S—Z (Y/Z = C, N, O or S). Structural relationships between monoclinic Na2SO3(H2O)7 and orthorhombic Na2CO3(H2O)7 are discussed in detail. |
