Phase formation studies and crystal structure refinements in the MnII/TeIV/O/(H) system

Systematic phase formation studies in the system Mn-II/Te-IV/O/-(H) using either solid-state reactions between stoichiometric MnO:TeO2 mixtures or hydrothermal reactions under basic conditions led to crystal growth of two polymorphs (alpha-, gamma-) of MnTeO3, Mn6Te5O16, Mn-15(TeO3)(14)(OH)(2) and Mn-3(TeO3)(2)(OH)(2). Although alpha-MnTeO3 and Mn6Te5O16 have been reported previously, crystal structure refinements were missing so far. Whereas alpha-MnTeO3 crystallizes in a unique structure (space group Pbca, Z=16), Mn6Te5O16 (Pnma, Z=4) is isotypic with its Co-homologue. The previously unknown phases gamma-MnTeO3 (Pbca, Z=8), Mn-15(TeO3)(14)(OH)(2) (R3? , Z=3) and Mn-3(TeO3)(2)(OH)(2) (P6(3)mc, Z=4) all have isotypic relationships, namely with ZnTeO3, Co-15(TeO3)(14)F-2 and M-3(TeO3)(2)(OH)(2) (M=Ni, Co), respectively. Common to all crystal structures of the five manganese(II) oxidotellurate(IV) phases is the presence of [MnO5] or [MnO6] polyhedra and isolated trigonal-pyramidal [TeO3] groups (except for one of the Te-IV atoms in Mn6Te5O16 [TeO4] bisphenoids) as principal building units, which share corners and edges with the [MnO5/6] groups. The resulting three-dimensional frameworks are dominated by the influence of the stereochemically active 5 s(2) electron lone pair situated at the Te-IV atom, leading to the formation of channels or interstices. Quantitative comparisons between the corresponding isotypic crystal structures are given.

Automated summary

Systematic studies in the Mn-II/Te-IV/O/-(H) system led to the successful synthesis of five manganese(II) oxidotellurate(IV) compounds. The crystal structures of these compounds were determined, and their relationships with other known compounds were analyzed.