Synthesis, spectroscopic characterization and crystal structures of thorium(IV) mononuclear lactato and hexanuclear formato complexes

Two thorium(Th) complexes with lactate or formate have been synthesized and characterized. Th(C3H5O3)4(H2O)2 (1) [C3H5O3H = lactic acid] has a mononuclear structure with ten-fold coordinated Th polyhedron in deformed bicapped square antiprism by four chelating lactate ligands via both carboxylate O and the alcohol O atoms in addition to two coordinated water molecules. The lactate ligands are enantiomer with equal proportion of R- and S-isomers. [Th6(O)4(OH)4(HCO2)12(H2O)6]·5H2O (2) [HCO2H = formic acid] is a hexanuclear Th nanocluster constructed by four oxo-, four hydroxyl, twelve μ2-bridging formate ligands and six water molecules. The calculated bond valence sums are in good agreement with the presence of equal numbers of oxo- and hydroxyl groups in the cluster. Thermal studies confirmed that both complexes lost water molecules first followed by the decomposition of the organic ligands to form ThO2 as the final product. The presence of bridging OH-groups in both complexes has been proven by Raman spectroscopy.