A novel route for the preparation of dimeric tetraorganodistannoxanes

The reaction of polymeric diorganotin oxides, (R2SnO)n (R=Me, Et, n-Bu, n-Oct, c-Hex, i-Pr, Ph), with saturated aqueous NH4X (X=F, Cl, Br, I, OAc) in refluxing 1,4-dioxane afforded in high yields dimeric tetraorganodistannoxanes, [R2(X)SnOSn(X)R2]2, and in a few cases diorganotin dihalides or diacetates, R2SnX2. The reported method appears suitable for the synthesis of fluorinated tetraorganodistannoxanes. Identification of [R2(OH)SnOSn(X)R2]2 (R=n-Bu; X=Cl, Br) and [R2(OH)SnOSn(X)R2] [R2(X)SnOSn(X)R2] suggest a serial substitution mechanism starting from [R2(OH)SnOSn(OH)R2]2. X-ray crystal structure determinations are reported for [Me2(AcO)SnOSn(OAc)Me2]2 (29a), [i-Pr2(Br)SnOSn(Br)i-Pr2]2 (20a), [c-Hex2(F)SnOSn(F)c-Hex2]2 (5a) and [c-Hex2(F)SnOSn(Cl)c-Hex2]2 (36), respectively. These show the presence of a central (R2Sn)2O2 core that is connected, via the oxygen atoms, to R2Sn entities. Acetate (29a) or halides (5a, 20a, 36) complete the coordination about the tin centres.