Thorium Chemistry in Oxo-Tellurium System under Extreme Conditions

Through the use of a high-temperature/high-pressure synthesis method, four thorium oxo-tellurium compounds with different tellurium valence states were isolated. The novel inorganic phases illustrate the intrinsic complexity of the actinide tellurium chemistry under extreme conditions of pressure and temperature. Th₂Te₃O₁₁ is the first instance of a mixed-valent oxo-tellurium compound, and at the same time, Te exhibits three different coordination environments (Te^IVO₃, Te^IVO₄, and Te^VIO₆) within a single structure. These three types of Te polyhedra are further fused together, resulting in a [Te₃O₁₁]^8- fragment. Na₄Th₂(Te^VI₃O₁₅) and K₂Th(Te^VIO₄)₃ are the first alkaline thorium tellurates described in the literature. Both compounds are constructed from ThO₉ tricapped trigonal prisms and Te^VIO₆ octahedra. Na₄Th₂(Te^VI₃O₁₅) is a three-dimensional framework based on Th₂O₁₅ and Te₂O₁₀ dimers, while K₂Th(Te^VIO₄)₃ contains tungsten oxide bronze like Te layers linked by ThO₉ polyhedra. The structure of β-Th(Te^IVO₃)(SO₄) is built from infinite thorium chains cross-linked by Te^IVO₃^2- and SO₄^2- anions. Close structural analysis suggests that β-Th(Te^IVO₃)(SO₄) is highly related to the structure of α-Th(SeO₄)₂. Additionally, the Raman spectra are recorded and the characteristic peaks are assigned based on a comparison of reported tellurites or tellurates.