A new structural form of tin as a double cube. A heptanuclear tin-sulfur cluster

Abstract

Recently, we reported new classes of organooxotin compounds in the form of cubes, ^1.2 drums,^3-6 and oxygen-capped cluster.^2,6,7 The faces of these clusters consist of either four- or six-membered Sn-O rings. The cube and the drum have the same empirical composition, [R'Sn(O)O₂PR₂]_n n = 4 and 6, respectively, whereas the oxygen-capped cluster, [(R'Sn(OH)O₂PR₂)₃O][R₂PO₂], resembles a cube with one corner missing. ¹¹⁹Sn NMR spectra show that the drum⁶ and the cube² forms undergo hydrolysis in solution giving oxygen-capped clusters. Heating the latter regenerates the starting drum⁶ or cube,⁸ thus showing the reaction to be reversible. In all of these compositions, tin is hexacoordinated, and chelating phosphinate or phosphate ligands span adjacent tin atoms.