Crystal structures of the penta- and hexa­hydrate of thulium nitrate

Tm(NO(3))(3)·5H(2)O and Tm(NO(3))(3)·6H(2)O, or more precisely [Tm(NO(3))(3)(H(2)O)(4)]·H(2)O and [Tm(NO(3))(3)(H(2)O)(4)]·2H(2)O, respectively, have been obtained from a concentrated solution of Tm(2)O(3) in HNO(3). The crystal structures of the two hydrates show strong similarities as both crystallize in space group P [Image: see text] with all atoms at general positions and contain neutral, mol­ecular [Tm(NO(3))(3)(H(2)O)(4)] complexes, i.e. ten-coordinated Tm(III) 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(NO(3))(3)·6H(2)O represents the maximally hydrated thulium nitrate as well as the heaviest rare earth nitrate hexa­hydrate known to date.