Peroxo-Thorium(IV)-Containing Heteropolytungstates and Their Oxo-Analogues: Synthesis, Structure and Solution Studies

High Resolution Image Download MS PowerPoint Slide We report the synthesis of peroxo-thorium(IV)-containing silico- and germanotungstates, [Th 3 (μ 3 -O 2 )(OH) 2 (H 2 O) 3 ( A- α-XW 9 O 34 ) 2 ] 12− (X = Si, Th 3 O 2 Si; Ge, Th 3 O 2 Ge ), prepared in aqueous solution via a straightforward two-step procedure: (1) reaction of thorium(IV) cations with trilacunary polytungstate precursors, followed by (2) the addition of hydrogen peroxide. In the absence of hydrogen peroxide, we were able to obtain the oxo-analogues, [Th 3 (μ 3 -O)(OH) 3 (H 2 O)( A- α-SiW 9 O 34 ) 2 ] 13– ( Th 3 Si ) and [Th 3 (μ 3 -O)(OH) 3 ( A- α-GeW 9 O 34 ) 2 ] 13– ( Th 3 Ge ), respectively. All four polyanions crystallized as hydrated mixed rubidium–sodium salts. Single-crystal X-ray diffraction revealed that the four polyanions Th 3 O 2 Si, Th 3 O 2 Ge, Th 3 Si, and Th 3 Ge consist of two { A- α-XW 9 O 34 } fragments sandwiching a central, triangular thorium core. The structures of Th 3 O 2 X (X = Si, Ge) comprise a central peroxo-group with a rare side-on μ 3 -coordination mode between the three thorium centers, representing the first example of peroxo-thorium(IV)-containing polyoxotungstates. Furthermore, 183 W NMR and electrochemical studies in solution were performed.