Thorium(IV) Molecular Clusters with a Hexanuclear Th Core

Three polynuclear thorium(IV) molecular complexes have been synthesized under ambient conditions from reactions of an amorphous Th precipitate, obtained via hydrolysis, with carboxylate functionalized ligands. The structures of Th-6(OH)(4)O-4-(H2O)(6)(HCO2)(12)center dot nH(2)O (1), Th-6(OH)(4)O-4(H2O)(6)(CH3CO2)(12)center dot nH(2)O (2), Th-6-(OH)(4)O-4(H2O)(6)(ClCH2CO2)(12)center dot 4H(2)O (3) each consist of a hexanuclear Th core wherein six 9-coordinate Th(IV) cations are bridged by four mu(3)-hydroxo and four mu(3)-oxo groups. Each Th(IV) center is additionally coordinated to one bound apical water molecule and four oxygen atoms from bridging carboxylate functionalized organic acid units. Decoration of the cationic [Th-6(mu(3)-O)(4)(mu(3)-OH)(4)](12+) cores by anionic shells of R-COO- ligands (R = H, CH3, or CH2Cl) terminates the oligomers and results in the formation of discrete, neutral molecular clusters. Electronic structure calculations at the density functional theory level predicted that the most energetically favorable positions for the protons on the hexanuclear core result in the cluster with the highest symmetry with the protons separated as much as possible. The synthesis, structure, and characterization of the materials are reported.