Crystal structures of two mononuclear complexes of terbium(III) nitrate with the tripodal alcohol 1,1,1-tris­(hy­droxy­meth­yl)propane

Two new mononuclear cationic complexes in which the Tb(III) ion is bis-chelated by the tripodal alcohol 1,1,1-tris­(hy­droxy­meth­yl)propane (H(3) L (Et), C(6)H(14)O(3)) were prepared from Tb(NO(3))(3)·5H(2)O and had their crystal and mol­ecular structures solved by single-crystal X-ray diffraction analysis after data collection at 100 K. Both products were isolated in reasonable yields from the same reaction mixture by using different crystallization conditions. The higher-symmetry complex dinitratobis[1,1,1-tris­(hy­droxy­meth­yl)propane]­terbium(III) nitrate di­meth­oxy­ethane hemisolvate, [Tb(NO(3))(2)(H(3) L (Et))(2)]NO(3)·0.5C(4)H(10)O(2), 1, in which the lanthanide ion is 10-coordinate and adopts an s-bicapped square-anti­prismatic coordination geometry, contains two bidentate nitrate ions bound to the metal atom; another nitrate ion functions as a counter-ion and a half-mol­ecule of di­meth­oxy­ethane (completed by a crystallographic twofold rotation axis) is also present. In product aqua­nitratobis[1,1,1-tris­(hy­droxy­meth­yl)propane]­terbium(III) dinitrate, [Tb(NO(3))(H(3) L (Et))(2)(H(2)O)](NO(3))(2), 2, one bidentate nitrate ion and one water mol­ecule are bound to the nine-coordinate terbium(III) centre, while two free nitrate ions contribute to charge balance outside the tricapped trigonal-prismatic coordination polyhedron. No free water mol­ecule was found in either of the crystal structures and, only in the case of 1, di­meth­oxy­ethane acts as a crystallizing solvent. In both mol­ecular structures, the two tripodal ligands are bent to one side of the coordination sphere, leaving room for the anionic and water ligands. In complex 2, the methyl group of one of the H(3) L (Et) ligands is disordered over two alternative orientations. Strong hydrogen bonds, both intra- and inter­molecular, are found in the crystal structures due to the number of different donor and acceptor groups present.