New insights in asymmetric tetraorganodistannoxane ladder formation. A NMR-spectroscopic and crystallographic study

The syntheses of the asymmetrically substituted tetraorganodistannoxanes [<i>t</i>-Bu₂(X)SnOSn(Y)(CH₂SiMe₃)₂1₂(<b>1</b>, X = Y = OH; <b>2</b>, X = Cl, Y = OH; <b>3</b>, X = Y = Cl) are reported and their structures in solution and in the solid state are characterized by multinuclear NMR spectroscopy and single crystal X-ray analyses. In toluene, the tetrahydroxy-substituted derivative <b>1</b> is in equilibrium with the organotin oxides <i>cyclo</i>-[<i>t</i>-Bu₂Sn{OSn(CH₂SiMe₃)₂}₂O] (<b>4</b>), <i>cyclo</i>[(Me₃SiCH₂)₂Sn(OSn<i>t</i>-Bu₂)₂O] (<b>5</b>), and <i>cyclo</i>-(<i>t</i>-Bu₂SnO)₃, and some additional, undefined species containing pentacoordinated tin atoms. In contrast, the dihydroxydichloro-substituted derivative <b>2</b> is inert in solution.<br />