An X-Ray Redetermination of the Crystal Structure of Tin(II) Chloride Dihydrate

Abstract

The crystal structure of tin(II) chloride dihydrate, SnCl₂·2H₂O has been redetermined by a single crystal X-ray diffractometer technique. The crystal is monoclinic, space group P2₁⁄c with a=9.313, b=7.250, c=8.970 Å, β=114°55′ and Z=4. The structure was solved by three-dimensional Patterson and electron density syntheses. An anisotropic least-squares refinement, based on 1695 independent reflections gave an R value of 0.04. The tin(II) atom forms a pyramidal complex with two chlorine atoms and one oxygen atom; the bond lengths in the pyramid are Sn–O, 2.33 and Sn–Cl, 2.50 and 2.56 Å and the bond angles are 86.9, 85.0, and 87.9°. These results support a view that the bonding in dichloroaquotin(II) complex is considerably ionic in character. This crystal consists of double layers of the aquocomplex, SnCl₂·(OH₂), parallel to (100) with intervening layers of the second water molecules. Both kinds of the water molecules are linked together by hydrogen bonds of 2.74, 2.79, and 2.80 Å into two-dimensional networks. The structure reported previously was found to be in error, although its essential feature was quite similar to the present one.