Hydrothermal synthesis, crystal structure, and characterization of tetrasodium tricobalt(II)-bis-phosphate-bis-hydrogenophosphate octahydrate, Na4Co3H2(PO4)(4)center dot 8H(2)O, with a new structure type

A sodium cobalt hydrogen phosphate hydrate, Na4Co3H2 (PO4)(4) . 8H(2)O, was synthesized by the mild hydrothermal method, and the crystal structure was characterized by the single-crystal X-ray diffraction method. The layered structure possesses a new type with the following data: Mr = 794.775, monoc linic, mP106, P2(1)/c-e26d (No. 14), a = 7.3547(9) Angstrom, b = 9.222(1) A ngstrom, c = 15.186(2) Angstrom, beta = 95.18(1)degrees, V = 1025.9(3) Angs trom(3), Z = 2, Dx = 2.573 g cm(-3), lambda = 0.71073 Angstrom, mu = 29.0 c m(-1), F(000) = 790, T = 293 K, R = 0.0346, wR = 0.0432 for 198 variables a nd 2278 contributing unique reflections. The structure is characterized by corner- and edge-sharing deformed CoO5 trigonal bipyramids with PO4 tetrahe dra forming an infinite ribbon along the [010] direction. The ribbons are c onnected by bridging CoO6 octahedra resulting in a novel three-cobalt polym eric coordination unit and a polyhedral sheet. The same sheets are packed a long the c-axis by sandwiching Na+ cations and hydrogen-bonded water molecu les to construct the whole structure. The temperature dependence of the mag netic susceptibility of the compound follows the Curie-Weiss law, and the e ffective magnetic moment of 4.69 mu(B) corresponds to high-spin Co2+ ion, c onfirmed by bond valence sum calculations. (C) 2000 Academic Press.