Dilithium hexahydroxidostannate(IV) dihydrate, a second monoclinic modification with a layer structure

Abstract

The title compound, Li2[Sn(OH)6]·2H 2O, is dimorphic. As for the previously described α-modification, the title β-modification crystallizes in the monoclinic system and contains the same primary building units, viz [Sn(OH) 6]2- octahedra and [Li(μ2-OH)3(H 2O)] tetrahedra. In contrast to the Sn - O bond lengths that are very similar in both modifications, the Li - O bond lengths differ significantly, in particular those involving the water molecule. In the new β-modification, the primary building units are linked into layers parallel to (010). The [Sn(OH)6]2- octahedra (-1 symmetry) form hexagonal nets and the [Li(μ2-OH)3(H2O)] tetrahedra are situated in between, with their apices in an alternating fashion up and down. O - H⋯O hydrogen bonds between OH groups and water molecules exist within the layers as well as between them.