Crystal structures of the penta- and hexahydrate of thulium nitrate

Abstract

Tm(NO3)3·5H2O and Tm(NO3)3·6H2O, or more precisely [Tm(NO3)3(H2O)4]·H2O and [Tm(NO3)3(H2O)4]·2H2O, respectively, have been obtained from a concentrated solution of Tm2O3 in HNO3. The crystal structures of the two hydrates show strong similarities as both crystallize in space group P\overline{1} with all atoms at general positions and contain neutral, molecular [Tm(NO3)3(H2O)4] complexes, i.e. ten-coordinated TmIII cations with three nitrate anions as bidentate ligands and four coordinating water molecules, and one or two additional crystal water molecules, respectively. All building units are connected by medium–strong to weak O—H...O hydrogen bonds. Tm(NO3)3·6H2O represents the maximally hydrated thulium nitrate as well as the heaviest rare earth nitrate hexahydrate known to date.