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Synthesis and Characterization of [Mo7O16(O3PCH2PO3)3]:8- A Mixed-Valent Polyoxomolybdenum Diphosphonate Anion with Octahedrally and Tetrahedrally Coordinated Molybdenum

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journal contribution
posted on 21.06.2002, 00:00 by Eddy Dumas, Capucine Sassoye, Kristin D. Smith, Slavi C. Sevov
Two new compounds containing the title diphosphono-polyoxometalate anion and diprotonated ethylenediamine (enH2) or piperazine (ppzH2) countercations have been hydrothermally synthesized and structurally characterized ((enH2)4[Mo7O16(O3PCH2PO3)3]·7H2O, triclinic, P1̄, Z = 2, a = 10.3455(7) Å, b = 13.136(1) Å, and c = 20.216(3) Å, α = 93.247(6)°, β = 96.434(6)°, and γ = 111.900(6)°; (ppzH2)4[Mo7O16(O3PCH2PO3)3]·8H2O, triclinic, P1̄, Z = 2, a = 13.255(2) Å, b = 13.638(2) Å, and c = 16.874(4) Å, α = 93.20(2)°, β = 101.27(2)°, and γ = 105.87(1)°). The anion is a ring of three pairs of edge-sharing octahedra of MoVO6 (with MoV−MoV bonds) that share corners with each other. The diphosphonate groups connect the pairs at the periphery. The ring is “capped” by a tetrahedron of MoVIO4. According to magnetic measurements, the compounds are diamagnetic.