Conversion of thorium(IV) oxide into thorium(IV) trifluoromethanesulfonate: Crystal structure of thorium(IV) trifluoromethanesulfonate dihydrate

The conversion of thorium(IV) oxide into thorium(IV) trifluoromethanesulfonate (triflate) in the concentrated aqueous solution of trifluoromethanesulfonic (triflic) acid under reflux condition was presented as a new simple method for dissolution of ThO2. In this method after refluxing and subsequent evaporation of water and triflic acid two forms of very hygroscopic solid thorium(IV) triflate salt were obtained: a greyish-white powder containing small amounts of triflic acid (with approximate composition of Th(CF3SO3)4·0.1CF3SO3H·2H2O, estimated by the TGA method), and colourless crystals of the [Th(CF3SO3)4(H2O)2]n formula. The last form has a polymeric structure in which thorium(IV) ion is surrounded by seven oxygen atoms from seven triflate ions and by two oxygen atoms from two water molecules, forming the ThO9 core with Thsingle bondO bond lengths in the range 2.371–2.516(3) Å. Thermal decomposition of both thorium(IV) triflate forms have led mainly to the formation of ThO2, which was confirmed by means of FIR, PXRD and XPS techniques.