A review of the structural architecture of tellurium oxycompounds

Abstract

Relative to its extremely low abundance in the Earth's crust, tellurium is the most mineralogically diverse chemical element, with over 160 mineral species known that contain essential Te, many of them with unique crystal structures. We review the crystal structures of 703 tellurium oxysalts for which good refinements exist, including 55 that are known to occur as minerals. The dataset is restricted to compounds where oxygen is the only ligand that is strongly bound to Te, but most of the Periodic 4+ cations display one-sided 3-, 4-or 5-coordination by oxygen (with rare examples of coordination numbers 2 and 6). For both valence states of Te, examples are known of Te m O n complexes which are monomeric (m = 1; neso), noncyclic finite oligomers (soro), rings (cyclo), infinite chains (ino), layers ( phyllo) and frameworks (tecto tellurates). There is a clear analogy to the polymerization classes that are known for silicate anions, but the behaviour of Te is much richer than that of Si for several reasons: (1) the existence of two cationic valence states for Te; (2) the occurrence of multiple coordination numbers; (3) the possibility of edge-sharing by TeO n polyhedra; (4) the possibility for oxygen ligands to be 3-coordinated by Te; and (5) the occurrence of Te m O n polymers that are cationic, as well as neutral or anionic. While most compounds contain only one or two symmetrically distinct types of Te atom, Pauling's Fifth Rule is frequently violated, and stoichiometrically simple compounds such as CaTeO 3 can have polymorphs with up to 18 distinct Te sites. There is a tendency for local symmetry features such as the threefold axis of a TeO 6 octahedron or the acentric symmetry of a Te 4+ O n polyhedron to be inherited by the host structure; the latter in particular can lead to useful physical properties such as nonlinear optical behaviour. We develop for the first time a hierarchical taxonomy of Te-oxysalt structures, based upon (1) valence state of Te; (2) polymerization state of Te m O n complexes; (3) polymerization state of larger strongly-bound structural units that include non-Te cations. Structures are readily located and compared within this classification.

Determination of the Correct Composition of “Hydrous Lead(II) Oxotellurate(IV)” as PbTeO3, Crystallizing as a New Polymorph

“…This type represents the most frequently observed coordination polyhedron of oxotellurates(IV) for which four-and five-coordinated Te IV atoms are also known [30,31]. The three Te-O bonds have lengths between 1.85 and 1.92 Å and three O-Te-O bond angles between 90° and 102°.…”

Redetermination of theγ-form of tellurium dioxide

“…Each TeO 4 polyhedron is linked to four symmetry-related TeO 4 polyhedra by sharing corners, which leads to the formation of a three-dimensional framework structure. Characteristic for the crystal chemistry of tellurium(IV) oxides or oxotellurates(IV) (Christy et al, 2016), the 5s 2 electron lone pair situated at the Te IV atom is stereochemically active and points towards the open space of this arrangement (Fig. 1).…”

The relationship between mineral composition, crystal structure and paragenetic sequence: the case of secondary Te mineralization at the Bird Nest drift, Otto Mountain, California, USA

“…Grundler et al, 2013). Further study is clearly justified, given that Te forms the largest number of mineral species of any element relative to its crustal abundance (Christy, 2015), shows an enormous diversity of crystal structural architecture in its minerals and synthetic compounds, whole groups of which are of interest for their photonic and fast-ion conduction properties (Christy et al, 2016), and is frequently an indicator of economic gold deposits in the crust (Cook et al, 2009).…”

“…While undertaking the review, we discovered that many Te compounds have reoccurring structural motifs (Christy et al, 2016) such as the Cu 2 Te ribbon found in frankhawthorneite , timroseite (Kampf et al, 2010e), paratimroseite (Kampf et al, 2010e) and bairdite (Kampf et al, 2013c), which suggested that Te oxysalt mineral structures form a structural hierarchy that might also correlate with paragenetic order, as do those noted above for other chemical classes of mineral. Testing this idea required a locality containing a large suite of Te minerals, and sufficient contact relationships between coexisting minerals for a paragenetic sequence to be deduced.…”

“…As part of a broader study of tellurium mineralogy, we have reinvestigated the stereochemistry of Te Christy and Mills, 2013), and undertaken a comprehensive review of the structural diversity of Te oxysalt compounds (Christy et al, 2016). While undertaking the review, we discovered that many Te compounds have reoccurring structural motifs (Christy et al, 2016) such as the Cu 2 Te ribbon found in frankhawthorneite , timroseite (Kampf et al, 2010e), paratimroseite (Kampf et al, 2010e) and bairdite (Kampf et al, 2013c), which suggested that Te oxysalt mineral structures form a structural hierarchy that might also correlate with paragenetic order, as do those noted above for other chemical classes of mineral.…”