A new heptanuclear tin cluster containing sulfur and oxygen in the framework

We have recently reported that new structural forms having the cube, (n-BuSn(O)O2PPh2)4, and oxygen-capped, [(n-BuSn(OH)O2PPh2)3O] [O2PPh2], formulations can be prepared by the reaction of n-butylstannonic acid with the corresponding diorganophosphinic acid. In new work exploring the effects of the bulky mesityl group bound to phosphorus, a cube formulation was also obtained. When n-butylstannonic acid was reacted with dicyclohexylphosphinic acid in the presence of nitric acid an oxygen-capped cluster having nitrate as the anion was obtained, demonstrating that the phosphinate anion is not required to stabilize the o-capped cation. In an attempt to generate similar structural forms, with sulfur replacing oxygen in the framework, the reaction of n-butylstannonic acid with diphenylphosphine oxide in the presence of elemental sulfur has been explored. From this reaction, a new structural form, containing seven hexacoordinate tin atoms and incorporating sulfur into the framework, [(n-BuSn(S)O2PPh2)3O]2Sn, was obtained in a mixture of products. A comparison of the crystal structures of the three compounds indicates that the new form has structural features in common with both the cube and the o-capped cluster