Crystal structure of polymeric tris(trimethyltin) chromate hydroxide

Crystals of the title compound are orthorhombic, space group Pbca, a= 20·85(2), b= 11·55(2), c= 16·58(2)Å(at ca. –30 °C), Z= 8. The structure was determined at ca. –30 °C from diffractometer data by direct methods and refined by full-matrix least-squares to R 0·045 for 488 unique observed reflexions. The structure consists of a complicated network polymer. There are three crystallographically independent and approximately planar tri-methyltin groups, and in each case, approximately trigonal bipyramidal co-ordination of the tin atom is completed by two axial oxygen atoms. Each oxygen atom in the chromate group is also bonded to tin, and the hydroxide group bridges two trimethyltin groups and is probably hydrogen bonded to one of the chromate oxygens. The two tin atoms linked by the hydroxide group have similar co-ordination geometries, with short Sn–O(H)[2.l4(3) and 2·17(4)Å] and long Sn–O(Cr)[2·48(5) and 2·51(4)Å]. The two oxygen atoms responsible for the long Sn–O bonds make the shortest two Cr–O bond lengths [1·61(4) and 1·56(4)Å]. Other bond lengths and angles are : Sn–O, 2·16(4) and 2·29(4); Cr–O, 1·78(4) and 1·70(4); mean Sn–C, 2·13 Å; mean C–Sn–C, 119; mean O–Sn–O, 176; mean Cr–O–Sn, 144; and Sn–O–Sn, 136(2)°.