Formation of nitrato-complexes during the solid state reaction between uranyl nitrate hexahydrate and rubidium nitrate polymerisation of the uranyl ion during the solid state reaction between uranyl nitrate hexahydrate and rubidium nitrate

Polymerised nitrato complexes of uranium (VI) and rubidium have been observed to form as intermediates during the solid state reaction between uranyl nitrate hexahydrate and rubidium nitrate at elevated temperatures. Reaction schemes have been proposed based on the simultaneous TG-DTA-EGA measurements on mixtures of the reactants and room-temperature X-ray diffraction data of the reaction intermediates prepared at various temperatures in the range 25-875 deg C. Uranyl nitrate hexahydrate dehydrated completely at 225 deg C in presence of rubidium nitrate to form anhydrous rubidium uranyl nitrate. The latter compound polymerised at temperatures above 350 deg C through oxygen bridging to form the rubidium uranyl oxy nitrato complexes, Rb2[(UO2)2(O)2(NO3)2] and Rb4[(UO2)3(O)4(NO3)2]. These complexes have been reported for the first time. Rb4[(UO2)3(O)4(NO3)2], formed above 460 deg C, decomposed at temperatures above 550 deg C to form the stable compound rubidium diuranate. (author)