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] [Fe-4(C2O4)(3) (HPO4)(2)(H2O)(2)] (1) and [(S)-C5H14 N-2] [Fe-4(C2O4)(3)(HPO4)(2)] (2), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction and MBssbauer spectroscopy. Crystal data are as follows: compound 1, triclinic, P1 (No. 1), a = 7.6999(4) Angstrom, b = 7.9542(4) Angstrom, c = 9.8262(5) Angstrom, alpha = 74.8444(7)degrees, beta = 81.7716(8)degrees, gamma = 85.4075(8)degrees, V = 574.34(8) Angstrom (3), Z = 1, and R1 = 0.0255; compound 2, monoclinic, P2(1) (No. 4), a = 7.5943(8) Angstrom, b = 7.8172(8) Angstrom, c = 18.318(2) Angstrom, beta = 99,111(2)degrees, V = 1073.8(3) Angstrom (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, (C) 2001 Academic Press.