Investigation of reactivity and structure formation in a K-Te-U oxo-system under high-temperature/high-pressure conditions.

The high-temperature/high-pressure treatment of the K-Te-U oxo-family at 1100 °C and 3.5 GPa results in the crystallization of a series of novel uranyl tellurium compounds, K2[(UO2)3(TeIVO3)4], K2[(UO2)TeO14], α-K2[(UO2)TeVIO5] and β-K2[(UO2)TeVIO5]. In contrast to most of the reported uranyl compounds which are favorable in layered structures, we found that under extreme conditions, the potassium uranyl oxo-tellurium compounds preferably crystallized in three-dimensional (3D) framework structures with complex topologies. Anion topology analysis indicates that the 3D uranyl tellurite anionic framework observed in K2[(UO2)3(TeIVO3)4] is attributable to the additional linkages of TeO3 polyhedra connecting with TeO4 disphenoids from the neighboring U-Te layers. The structure of K2[(UO2)TeO14] can be described based on [UTe6O26]22- clusters, where six TeO5 polyhedra enclose a hexagonal cavity in which a UO8 polyhedron is located. The [UTe6O26]22- clusters are further linked by TeO5 square pyramids to form the 3D network. Similar to uranyl tellurates, both α-K2[(UO2)TeVIO5] and β-K2[(UO2)TeVIO5] contain TeO6 octahedra which share a common face to form a dimeric Te2O10 unit. However, in α-K2[(UO2)TeVIO5], these Te2O10 units connect with UO6 tetragonal bipyramids to form a 3D structural framework, while in β-K2[(UO2)TeVIO5], the same Te2O10 dimers are observed to link with UO7 pentagonal bipyramids, forming 2D layers. Raman measurements were carried out and the vibration bands related to TeIV-O, TeVI-O and UVI-O bonds are discussed.