Anion‐Selectivity of Distannyl Derivatives in MembranesA series of distannyl derivatives (2,2‐bis(trimethylstannyl)‐1,3‐dithiane, 2,2‐bis(tributylstannyl)‐1,3‐dithiane, hexamethyldistannane, hexabutyldistannane, hexaphenyldistannane, bis(triphenylstannyl)sulfide,o‐bis(trimethylstannyl)benzene) has been studied in view of their applicability as anion‐selective ionophores in solvent polymeric membranes. None of these compounds induces significant changes in the anion‐selectivity pattern as compared with the membranes containing no organotin compound. Representatives with tributylstannyl groups, however, undergo chemical reactions leading to highly active anion ionophores of the type Bu3SnX, several of which (e.g.Bu3SnCl and Bu3SnOH) may be present in equilibrium in the membrane phase depending on the m