| Abstract: | Cs2(H3O)Pr(CH3COO)6 and Cs2Pr(CH3COO)5: Synthesis, Crystal Structures and Thermolysis. Analogous Acetates with Lanthanum through Terbium Single crystals of Cs2(H3O)Pr(CH3COO)6 are obtained as green plates from an acetic acid solution (≈50%) of Cs2CO3 and Pr(CH3COO)3 · 1,5 H2O. The crystal structure monoclinic, Cm, Z = 2, a = 1 540.4(4), b = 691.3(2), c = 1 221.5(4) pm, β = 104.60(5)°, Vm = 379.1(2) cm3/mol, R = 0.040, Rw = 0.035 was determined from four-circle-diffractometer data. The structure consists of monomeric Pr(CH3COO)3 units, in which Pr3+ is surrounded by nine oxygen atoms. These monomers are linked together to infinite layers parallel (001) by common acetate oxygen atoms with two ?molecules”? of Cs(CH3COO). Together with an additional acetate ion coordinated to one of the Cs+ ions the composition of the layers is Cs2Pr(CH3COO)6]?. Between these layers H3O+ is located for electroneutrality. Thermal decomposition of Cs2(H3O)Pr(CH3COO)6 was examined with thermoanalytical methods (TG/DTA with coupled gas analysis), Guinier-Simon technique and IR spectroscopy: beginning at 70°C the compound looses water and acetic acid. It decomposes topotactically to Cs2Pr(CH3COO)5. At 270°C this acetate decomposes to Cs2CO3 and Pr2O2CO3 which emits CO2 at 600°C form ing Pr2O3or PrO2?x Single crystals of Cs2Pr(CH3COO)5 were obtained from Pr(CH3COO)3, in molten Cs(CH3COO) at about 200°C. The crystal structure tetragonal, P43, Z = 4, a = 1 174,5(2), c = 1 480,5(3) pm, Vm = pin,307,5(1) cm3/mol, R = 0,061, Rw= 0,031 again consists of Pr(CH3COO)3, monomers where Pr3+ has 9 oxygen ligands in its first coordination sphere. They are linked together by two ”molecules“ of cesium acetate to infinite chains along 00l] around the 4, screw axis. There are also acetate bridges between these chains. Isotypic compounds Cs2(H3O)M(CH3COO)6 and Cs2M(CH3COO)5, and Cs2M(CH3COO)5with M = La? Tb, were obtained from acetic acid solutions or thermal decomposition and were characterized by X-ray Guinier techniques. |
