Synthesis and Characterization of a New Bisphosphonic Acid and Several Metal Hybrids Derivatives

Commercial bis-(4-bromophenyl)-ether, [BrC6H4]2−O, has been used to prepare 4-[4‘-(diethoxyphosphoryl)phenoxy]phenyl-phosphonic acid diethyl ester, [(CH3CH2)2O3P−C6H4]2−O, (I) following a slight modification of the
Michaelis−Arbuzov reaction. The acid hydrolysis of I gave 4-(4‘-phosphonophenoxy)phenyl phosphonic acid,
[H2O3P−C6H4]2−O (II), and both compounds have been characterized by 1H NMR and 13C NMR. The crystal structure
of II has been determined by single-crystal X-ray diffraction. II crystallizes in an orthorhombic unit cell, space group
Pbcn, with a = 7.822(3) Å, b = 5.821(2) Å, c = 28.982(9) Å, and V = 1319.7(7) Å3. The final R factor was R1
= 0.0614. The structure is layered, being held together through a hydrogen bonding network. II has been used as
precursor in the syntheses of new metal (Mn, Fe, Co, Ni, Cu, and Zn) bisphosphonates. The syntheses were
carried out using a fixed metal/bisphosphonic acid molar ratio of 2.1:1 and the influence of the pH in the reactions has been studied. Nine new compounds have been isolated:  Mn2(O3PC6H4OC6H4PO3)·1.5H2O (III),
Mn5(OH)2(O3PC6H4OC6H4PO3)2·2H2O (IV), Fe(HO3PC6H4OC6H4PO3)·0.5H2O (V), Co2(O3PC6H4OC6H4PO3)·2H2O
(VI), Ni2(O3PC6H4OC6H4PO3)·3H2O (VII), Ni2(O3PC6H4OC6H4PO3)·2H2O (VIII), Cu2(O3PC6H4OC6H4PO3) (IX),
Zn2(O3PC6H4OC6H4PO3) (X), and Zn(HO3PC6H4OC6H4PO3H) (XI). Compound IX crystallizes in an orthorhombic
unit cell, space group Pbcn, and unit cell parameters a = 8.1012(5) Å, b = 5.3109(3) Å, c = 29.2595(5) Å, and
V = 1258.8(1) Å3. Its structure has been solved by ab initio powder diffraction and refined by the Rietveld method
to RF = 0.042. IX has a pillared layer framework with highly distorted CuO5 groups sharing edges to give isolated
dimers. XI was indexed in a monoclinic unit cell, space group P1121, with parameters a = 9.4991(9) Å, b =
5.0445(5) Å, c = 29.131(2) Å, γ = 91.945(7)°, and V = 1395.1(3) Å3. Its structure has been refined by the
Rietveld method, RF = 0.054, since it is isostructural with the known compound, Zn[HO3P(C6H4)2PO3H]. All solids
were also characterized by thermal analysis and IR and UV−Vis spectroscopies.