Synthesis and Characterization of New Iron Phosphatooxalates: [(S)-C5H14N2] [Fe4(C2O4)3(HPO4)2(H2O)2] and [(S)C5H14N2] [Fe4(C2O4)3(HPO4)2]

Two new organically templated iron(II) phosphatooxalates, [(S)-C5H14N2] [Fe4(C2O4)3(HPO4)2(H2O)2] (1) and [(S)C5H14 N2] [Fe4(C2O4)3(HPO4)2] (2), have been synthesized under hydrothermal conditions and characterized by singlecrystal X-ray diffraction and M?ssbauer spectroscopy. Crystal data are as follows: compound 1, triclinic, P1 (No. 1), a= 7.6999(4) ?, b=7.9542(4) ?, c=9.8262(5) ?, =74.8444(7)°, =81.7716(8)°, =85.4075(8)°, V=574.34(8) ?3, Z=1, and R1 =0.0255; compound 2, monoclinic, P21 (No. 4), a=7.5943(8) ?, b=7.8172(8) ?, c=18.318(2) ?, =99.111(2)°, V=1073.8 (3) ?3, Z=2, and R1=0.0281. The structure of 1 consists of dimers of edge-sharing FeO6 octahedra that are linked by phosphate and oxalate groups to generate a three-dimensional framework with intersecting tunnels parallel to the [100] and [010] directions. Diprotonated (S)-2-methylpiperazinium cations are located at the intersections of these tunnels. Compound 1 crystallizes as a minor product when a racemic mixture of 2-methylpiperazine is used in the synthesis, and can be prepared as a major product with a small amount of 2 if optically pure (S)-2-methylpiperzine is used. The structure of 2 is similar to that of 1 except that the coordination around the iron centers in the dimer are square pyramidal and octahedral. The two compounds are the first 3-dimensional phosphatooxalates containing a chiral amine.