Hydrothermal synthesis and characterization of an ethylenediamine-templated mixed-valence titanium phosphate

The mixed-valence compound (TiTiIV)-Ti-III(HPO4)(4). C2N2H9. H2O (1) is syn thesized hydrothermally from titanium powder, phosphoric and boric acids, a nd ethylenediamine. The compound is structurally stable up to 650 degrees C . It loses the template and the water molecule above 250 degrees C, all tit anium becomes Ti-IV at 600 degrees C, and the result is the new compound (T iTiIV)-Ti-IV(HPO4)(4) (2). The structures of the two compounds were determi ned ab initio from powder diffraction data. Crystal data: (TiTiIV)-Ti-III(H PO4)(4). C2N2H9. H2O, I4(1), a = 6.371(2), 16.571(1) Angstrom,V = 672.5(1) Angstrom(3), Z = 2; (TiTiIV)-Ti-IV(HPO4)(4), I4(1)/a, a = 6.335(2), c = 16. 389(1) Angstrom, V = 657.7(1) Angstrom(3), Z = 2. Both structures are of th e open type, and the frameworks are nearly identical. Compound 2, tau-Ti(HP O4)(2), is the first three-dimensional titanium hydrogen phosphate. Results of magnetization, TGA, BET, X-ray thermodiffractometry, and density measur ements are also presented.