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

## TL;DR

This paper describes the synthesis and structural analysis of new thorium-containing polyoxotungstates with and without peroxide groups.

## Contribution

The first example of peroxo-thorium(IV)-containing polyoxotungstates with a rare side-on μ3-coordination mode is reported.

## Key findings

- The new polyanions were synthesized using a two-step aqueous procedure involving thorium(IV) cations and polytungstate precursors.
- X-ray diffraction revealed a triangular thorium core sandwiched between two polytungstate fragments in all four compounds.
- 183W NMR and electrochemical studies confirmed structural and solution properties of the synthesized compounds.

## Abstract

We report the synthesis of peroxo-thorium­(IV)-containing
silico-
and germanotungstates, [Th3(μ3-O2)­(OH)2(H2O)3(A-α-XW9O34)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,
[Th3(μ3-O)­(OH)3(H2O)­(A-α-SiW9O34)2]13– (Th

3

Si) and [Th3(μ3-O)­(OH)3(A-α-GeW9O34)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-XW9O34} 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 μ3-coordination mode between the three thorium centers, representing
the first example of peroxo-thorium­(IV)-containing polyoxotungstates.
Furthermore, 183W NMR and electrochemical studies in solution
were performed.