Hydrothermal Synthesis and Characterization of New Pillared Layered Ethylenediphosphonates of Molybdenum(VI), A₂[Mo₂O₅(O₃PCH₂CH₂PO₃)] (A = NH₄, Tl, Cs, Rb) and K(H₃O)[Mo₂O₅(O₃PCH₂CH₂PO₃)]

New ethylenediphosphonates of molybdenum, A₂[Mo₂O₅(O₃PCH₂CH₂PO₃)] (A = NH₄ (1), Tl (2), Cs (3), Rb (4)), and K(H₃O)[Mo₂O₅(O₃PCH₂CH₂PO₃)] (5), have been synthesized by a hydrothermal method and structurally characterized by X-ray diffraction, spectroscopic, and thermal studies. These compounds consist of pillared anionic layers [Mo₂O₅(O₃PCH₂CH₂PO₃)]^2-, with A⁺, K⁺, and H₃O⁺ ions in the interlayer region as well as in the cavities within the anionic layers. Single-crystal X-ray structures of compounds 1 and 5 have been determined. They crystallize in the orthorhombic space group Cmca with Z = 8 and have the following unit cell parameters. For 1, a = 25.60(1), b = 10.016(4), and c = 9.635(3) Å and for 5, a = 25.63(1), b = 10.007(2), and c = 9.512(1) Å.