Alkyltin halides and related compounds, R_4–nSnX_n(n= 1–3, R = Me, Et, or Bu), react with polymeric dialkyltin oxides, R′₂SnO (R′= Me, Et, Bu, octyl, or Ph), to give functionally substituted distannoxanes, X_n–1R_4–nSn·O·- SnR′₂X; in the presence of moisture, tin tetrachloride reacts to give the dialkyltrichlorohydroxydistannoxanes, X₂(HO)Sn·O·SnR′₂X. These reactions represent formally the insertion of an R₂SnO unit into the Sn–X bond. Similar reactions between dibutyltin dichloride or butyltin trichloride and an excess of dibutyltin oxide give functionally substituted oligostannoxanes.