Incorporation of Sulfate or Selenate Groups into Oxotellurates(IV): I. Calcium, Cadmium, and Strontium Compounds

Abstract

Seven new mixed oxochalcogenate compounds in the systems M II /X VI /Te IV /O/(H), (M II = Ca, Cd, Sr; X VI = S, Se) were obtained under hydrothermal conditions (210°C, one week). Crystal structure determinations based on single-crystal X-ray diffraction data revealed the compositions Ca 3 (3 ) 2 are metal-oxotellurate(IV) layers connected by bridging XO 4 tetrahedra and/or by hydrogen-bonding interactions involving hydroxyl or water groups, whereas Cd 4 (SO 4 )(TeO 3 ) 3 and Cd 5 (SO 4 ) 2 (TeO 3 ) 2 (OH) 2 crystallize as framework structures. Common to all crystal structures is the stereoactivity of the Te IV electron lone pair for each oxotellurate(IV) unit, pointing either into the inter-layer space, or into channels and cavities in the crystal structures.

Incorporation of Sulfate or Selenate Groups into Oxotellurates(IV): II. Compounds with Divalent Lead

“…As previously pointed out, multi‐phase formation of hydrothermally synthesized products is a common observation and also applies for the present Pb II / X VI /Te IV /O/(C) ( X = S and Se) systems. All experiments resulted in the formation of multi‐phase products; representative batches with reagents used and product phases determined are compiled in Table .…”

“…All experiments resulted in the formation of multi‐phase products; representative batches with reagents used and product phases determined are compiled in Table . Just like in the related systems M II / X VI /Te IV /O, where lead is replaced by divalent metals of comparable size ( M = Ca, Sr, Cd, Hg, ), in the present study compounds containing both tellurium and sulfur/selenium are minority products, whereas compounds containing tellurium as the only chalcogen are majority products. Likewise, formation of Te‐ and S/Se‐containing phases becomes more successful at basic conditions (pH 9–11), which also explains the formation of the “basic” compound Pb 7 O 4 (SeO 4 ) 2 (TeO 3 ) (for a discussion of “basic” features in this compound, see below).…”

“…In continuation of our previous investigations on the effect of introducing tetrahedral oxochalcogenate(VI) anions as spacers into framework structures of divalent metal oxotellurates(IV) (metal = mercury, cadmium, calcium, strontium), to possibly obtain compounds with non‐centrosymmetric structures, we have expanded these studies to lead(II) oxotellurates(IV). Next to the structure‐directing, i.e.…”

Phase Formation Studies of Lead(II) Copper(II) Oxotellurates: The Crystal Structures of Dimorphic PbCuTeO5, PbCuTe2O6, and [Pb2Cu2(Te4O11)](NO3)2

“…For example, incorporation of cadmium into a lead(II) oxotellurate(VI) resulted in the non‐centrosymmetric structure of Pb 6 CdTeO 10 , just like the addition of tetrahedral building blocks (e.g. SO 4 2– of sulfates, or SeO 4 2– of selenates) in lead(II) or other divalent metal oxotellurates(IV) led to formation of some compounds without an inversion center …”

Redetermination of theγ-form of tellurium dioxide

“…In a continuation of hydrothermal phase formation studies to incorporate tetrahedral XO 4 groups (X = S, Se) into framework structures of divalent metal oxotellurates(IV) (metal = Ca, Cd, Hg, Mg, Pb, Sr, Zn; Weil & Shirkhanlou, 2015, 2017a, the system Mn/Se/Te/O was investigated. In one of these experiments, single crystals of -TeO 2 were obtained serendipitously as a minor by-product.…”