Synthesis of trans-1,2-difluoroethenediylbis(phosphonic acid) and other unsaturated phosphonic acids

Article abstract of DOI:10.1021/ja00164a042

The phosphonic acids (HO)₂P(O)CF=CFP(O)(OH)₂, CF₂=CFCH₂CH₂P(O)(OH)₂, and (HO)₂P(O)C=CP-(O)(OH)₂(CF₂)_nCF ₂ (n = 1, 3) have been synthesized for the first time. trans-1,2-Difluoroethenediylbis(phosphonic acid) was prepared from (C₂H₅O)₂P(O)CFBrCFBrP(O)(OC₂H ₅)₂, which had been obtained via coupling of the corresponding sulfinate salt, (C₂H₅O)₂P(O)CFBrSO₂Na, by adding 30% aqueous hydrogen peroxide to a solution Of(C₂H₅O)₂P(O)CFBrSO₂Na and iron(II) sulfate. The X-ray crystal structure of the salt [Zn(H₂O)₆]²⁺[O(HO)P(O)CF=CFP(O)(OH)O] ^2- indicates a network of [Zn(H₂O)₆]²⁺ dications and the acid dianions linked together with water molecules via hydrogen bonding. The phosphorus, fluorine, and carbon atoms are coplanar.