Tellurium compounds are compounds containing the element tellurium (Te). Tellurium belongs to the chalcogen (group 16) family of elements on the periodic table, which also includes oxygen, sulfur, selenium and polonium: Tellurium and selenium compounds are similar. Tellurium exhibits the oxidation states −2, +2, +4 and +6, with +4 being most common.[1]
Reduction of Te metal produces the tellurides and polytellurides, Ten2−. The −2 oxidation state is exhibited in binary compounds with many metals, such as zinc telluride, ZnTe, produced by heating tellurium with zinc.[2] Decomposition of ZnTe with hydrochloric acid yields hydrogen telluride (H 2Te), a highly unstable analogue of the other chalcogen hydrides, H 2O, H 2S and H 2Se:
ZnTe + 2 HCl → ZnCl 2 + H 2Te
H 2Te is unstable, whereas salts of its conjugate base [TeH]− are stable.
Halides
Structure of tellurium tetrachloride, tetrabromide and tetraiodide
The +2 oxidation state is exhibited by the dihalides, TeCl 2, TeBr 2 and TeI 2. The dihalides have not been obtained in pure form,[3]:274 although they are known decomposition products of the tetrahalides in organic solvents, and the derived tetrahalotellurates are well-characterized:
Te + X 2 + 2 X− → TeX2− 4
where X is Cl, Br, or I. These anions are square planar in geometry.[3]:281 Polynuclear anionic species also exist, such as the dark brown Te 2I2− 6,[3]:283 and the black Te 4I2− 14.[3]:285
With fluorine Te forms the mixed-valenceTe 2F 4 and TeF 6. In the +6 oxidation state, the –OTeF 5 structural group occurs in a number of compounds such as HOTeF 5, B(OTeF 5) 3, Xe(OTeF 5) 2, Te(OTeF 5) 4 and Te(OTeF 5) 6.[4] The square antiprismatic anion TeF2− 8 is also attested.[5] The other halogens do not form halides with tellurium in the +6 oxidation state, but only tetrahalides (TeCl 4, TeBr 4 and TeI 4) in the +4 state, and other lower halides (Te 3Cl 2, Te 2Cl 2, Te 2Br 2, Te 2I and two forms of TeI). In the +4 oxidation state, halotellurate anions are known, such as TeCl2− 6 and Te 2Cl2− 10. Halotellurium cations are also attested, including TeI+ 3, found in TeI 3AsF 6.[6]
Oxocompounds
A sample of tellurium dioxide powder
Tellurium monoxide was first reported in 1883 as a black amorphous solid formed by the heat decomposition of TeSO 3 in vacuum, disproportionating into tellurium dioxide, TeO 2 and elemental tellurium upon heating.[7][8] Since then, however, existence in the solid phase is doubted and in dispute, although it is known as a vapor fragment; the black solid may be merely an equimolar mixture of elemental tellurium and tellurium dioxide.[9]
Tellurium dioxide is formed by heating tellurium in air, where it burns with a blue flame.[2] Tellurium trioxide, β-TeO 3, is obtained by thermal decomposition of Te(OH) 6. The other two forms of trioxide reported in the literature, the α- and γ- forms, were found not to be true oxides of tellurium in the +6 oxidation state, but a mixture of Te4+ , OH− and O− 2.[10] Tellurium also exhibits mixed-valence oxides, Te 2O 5 and Te 4O 9.[10]
The tellurium oxides and hydrated oxides form a series of acids, including tellurous acid (H 2TeO 3), orthotelluric acid (Te(OH) 6) and metatelluric acid ((H 2TeO 4) n).[9] The two forms of telluric acid form tellurate salts containing the TeO2– 4 and TeO6− 6 anions, respectively. Tellurous acid forms tellurite salts containing the anion TeO2− 3.
Other chalcogenides
A disulfide, TeS2, forms when tellurous acid (H2TeO3) is mixed with hydrogen sulfide, but is unstable above −20°C.[11] In contrast, many thiotellurate anions are known, including TeS2−3, Te(S5)x(S7)2- y (x + y = 2). Many of these arise from the action of tellurium metal on polysulfide anions,[12][13] although a solid-state synthesis is also possible.[14] Despite their similarities to sulfo-selenide anions, the thiotellurates are not catenation products; instead, the sulfur ligands coordinate to the tellurium as heavier congeners to a tellurate.[15] A thiosubtellurite, TeS2−2, is also known. These compounds are of interest because of their potential for ionic conductivity.[16]
Analogous selenotellurates are also known.
Zintl cations
When tellurium is treated with concentrated sulfuric acid, the result is a red solution of the Zintl ion, Te2+ 4.[17] The oxidation of tellurium by AsF 5 in liquid SO 2 produces the same square planar cation, in addition to the trigonal prismatic, yellow-orange Te4+ 6:[5]
4 Te + 3 AsF 5 → Te2+ 4(AsF− 6) 2 + AsF 3
6 Te + 6 AsF 5 → Te4+ 6(AsF− 6) 4 + 2 AsF 3
Other tellurium Zintl cations include the polymeric Te2+ 7 and the blue-black Te2+ 8, consisting of two fused 5-membered tellurium rings. The latter cation is formed by the reaction of tellurium with tungsten hexachloride:[5]
8 Te + 2 WCl 6 → Te2+ 8(WCl− 6) 2
Interchalcogen cations also exist, such as Te 2Se2+ 6 (distorted cubic geometry) and Te 2Se2+ 8. These are formed by oxidizing mixtures of tellurium and selenium with AsF 5 or SbF 5.[5]
Tellurium does not readily form analogues of alcohols and thiols, with the functional group –TeH, that are called tellurols. The –TeH functional group is also attributed using the prefix tellanyl-.[18] Like H2Te, these species are unstable with respect to loss of hydrogen. Telluraethers (R–Te–R) are more stable, as are telluroxides.
Tritelluride quantum materials
Recently, physicists and materials scientists have been discovering unusual quantum properties associated with layered compounds composed of tellurium that's combined with certain rare-earth elements, as well as yttrium (Y).[19]
These novel materials have the general formula of R Te3, where "R " represents a rare-earth lanthanide (or Y), with the full family consisting of R = Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er & Tm (not yet observed are compounds containing Pm, Eu, Yb & Lu). These materials have a two-dimensional character within an orthorhombic crystal structure, with slabs of R Te separated by sheets of pure Te.[19]
It is thought that this 2-D layered structure is what leads to a number of interesting quantum features, such as charge-density waves, high carrier mobility, superconductivity under specific conditions, and other peculiar properties whose natures are only now emerging.[19]
For example, in 2022, a small group of physicists at Boston College in Massachusetts led an international team that used optical methods to demonstrate a novel axial mode of a Higgs-like particle in R Te3 compounds that incorporate either of two rare-earth elements (R = La, Gd).[20] This long-hypothesized, axial, Higgs-like particle also shows magnetic properties and may serve as a candidate for dark matter.[21]
The chalcogens are the chemical elements in group 16 of the periodic table. This group is also known as the oxygen family. Group 16 consists of the elements oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and the radioactive elements polonium (Po) and livermorium (Lv). Often, oxygen is treated separately from the other chalcogens, sometimes even excluded from the scope of the term "chalcogen" altogether, due to its very different chemical behavior from sulfur, selenium, tellurium, and polonium. The word "chalcogen" is derived from a combination of the Greek word khalkόs (χαλκός) principally meaning copper, and the Latinized Greek word genēs, meaning born or produced.
Tellurium is a chemical element with the symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally found in its native form as elemental crystals. Tellurium is far more common in the Universe as a whole than on Earth. Its extreme rarity in the Earth's crust, comparable to that of platinum, is due partly to its formation of a volatile hydride that caused tellurium to be lost to space as a gas during the hot nebular formation of Earth.
The telluride ion is the anion Te2− and its derivatives. It is analogous to the other chalcogenide anions, the lighter O2−, S2−, and Se2−, and the heavier Po2−.
Selenic acid is the inorganic compound with the formula H2SeO4. It is an oxoacid of selenium, and its structure is more accurately described as O2Se(OH)2. It is a colorless compound. Although it has few uses, one of its salts, sodium selenate is used in the production of glass and animal feeds.
In chemistry tellurate is a compound containing an oxyanion of tellurium where tellurium has an oxidation number of +6. In the naming of inorganic compounds it is a suffix that indicates a polyatomic anion with a central tellurium atom.
Telluric acid, or more accurately Orthotelluric acid, is a chemical compound with the formula Te(OH)6, often written as H6TeO6. It is a white crystalline solid made up of octahedral Te(OH)6 molecules which persist in aqueous solution. In the solid state, there are two forms, rhombohedral and monoclinic, and both contain octahedral Te(OH)6 molecules, containing one hexavalent tellurium (Te) atom in the +6 oxidation state, attached to six hydroxyl (–OH) groups, thus, it can be called tellurium(VI) hydroxide. Telluric acid is a weak acid which is dibasic, forming tellurate salts with strong bases and hydrogen tellurate salts with weaker bases or upon hydrolysis of tellurates in water. It is used as tellurium-source in the synthesis of oxidation catalysts.
A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS2 is a common solid lubricant.
Selenium dioxide is the chemical compound with the formula SeO2. This colorless solid is one of the most frequently encountered compounds of selenium.
Tellurium hexafluoride is the inorganic compound of tellurium and fluorine with the chemical formula TeF6. It is a colorless, highly toxic gas with an unpleasant odor.
Teflic acid is the chemical compound with the formula HOTeF5. This strong acid is related to orthotelluric acid, Te(OH)6. Teflic acid has a slightly distorted octahedral geometry.
Hydrogen telluride is the inorganic compound with the formula H2Te. A hydrogen chalcogenide and the simplest hydride of tellurium, it is a colorless gas. Although unstable in ambient air, the gas can exist at very low concentrations long enough to be readily detected by the odour of rotting garlic at extremely low concentrations; or by the revolting odour of rotting leeks at somewhat higher concentrations. Most compounds with Te–H bonds (tellurols) are unstable with respect to loss of H2. H2Te is chemically and structurally similar to hydrogen selenide, both are acidic. The H–Te–H angle is about 90°. Volatile tellurium compounds often have unpleasant odours, reminiscent of decayed leeks or garlic.
Selenium tetrafluoride (SeF4) is an inorganic compound. It is a colourless liquid that reacts readily with water. It can be used as a fluorinating reagent in organic syntheses (fluorination of alcohols, carboxylic acids or carbonyl compounds) and has advantages over sulfur tetrafluoride in that milder conditions can be employed and it is a liquid rather than a gas.
Sodium telluride is the chemical compound with the formula Na2Te. This salt is the conjugate base of the thermally unstable acid hydrogen telluride, but it is usually prepared by reduction of tellurium with sodium. Na2Te is a challenging material to handle because it is very sensitive to air. Air oxidizes it initially to polytellurides, which have the formula Na2Tex (x > 1), and ultimately Te metal. Samples of Na2Te, which are colourless when absolutely pure, generally appear purple or dark gray due to the effects of air oxidation.
Selenium trioxide is the inorganic compound with the formula SeO3. It is white, hygroscopic solid. It is also an oxidizing agent and a Lewis acid. It is of academic interest as a precursor to Se(VI) compounds.
Selenium compounds commonly exist in the oxidation states −2, +2, +4, and +6.
Gold chalcogenides are compounds formed between gold and one of the chalcogens, elements from group 16 of the periodic table: oxygen, sulfur, selenium, or tellurium.
In chemistry, molecular oxohalides (oxyhalides) are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element A in a single molecule. They have the general formula AOmXn, where X is a halogen. Known oxohalides have fluorine (F), chlorine (Cl), bromine (Br), and/or iodine (I) in their molecules. The element A may be a main group element, a transition element, a rare earth element or an actinide. The term oxohalide, or oxyhalide, may also refer to minerals and other crystalline substances with the same overall chemical formula, but having an ionic structure.
The chalcogens react with each other to form interchalcogen compounds.
Molybdenum(IV) telluride, molybdenum ditelluride or just molybdenum telluride is a compound of molybdenum and tellurium with formula MoTe2, corresponding to a mass percentage of 27.32% molybdenum and 72.68% tellurium. It can crystallise in two dimensional sheets which can be thinned down to monolayers that are flexible and almost transparent. It is a semiconductor, and can fluoresce. It is part of a class of materials called transition metal dichalcogenides. As a semiconductor the band gap lies in the infrared region. This raises the potential use as a semiconductor in electronics or an infrared detector.
Chalcogenidotetrelates are chemical compounds containing a group 14 element, known as a tetrel, and a group 16 element, known as a chalcogen. The group 14 elements are carbon, silicon, germanium, tin, lead and flerovium. Flerovium compounds like this are unknown due to its short half-life. The group 16 elements are oxygen, sulfur, selenium, tellurium, polonium and livermorium. Livermorium compounds like this are unknown due to its short half-life. Chalcogenidotetrelates are a class of chalcogenidometalates. In chalcogenidotetrelates, the chalcogen atom is normally divalent, and the tetrel atom is normally tetravalent. The chalcogen atom has one or two single bonds, or one double bond to tetrel atoms. The tetrel atom has one, two, three or four single bonds to chalcogen atoms, or one double bond plus one or two single bonds to chalcogen atoms. The tetrel atom would normally have four bonds in a +4 oxidation state. Carbon differs significantly from the other elements in seldom having four single bonds to chalcogens, and so has few compounds in this class such as orthocarbonates.
References
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1 2 3 4 Emeleus, H. J. (1990). A. G. Sykes (ed.). Advances in Inorganic Chemistry. Vol.35. Academic Press. ISBN0-12-023635-4.
↑ Holloway, John H.; Laycock, David (1983). "Preparations and Reactions of Inorganic Main-Group Oxide-Fluorides". In Harry Julius Emeléus; A. G. Sharpe (eds.). Advances in inorganic chemistry and radiochemistry. Serial Publication Series. Vol.27. Academic Press. p.174. ISBN0-12-023627-3.
1 2 3 4 Wiberg, Egon; Holleman, Arnold Frederick (2001). Nils Wiberg (ed.). Inorganic chemistry. translated by Mary Eagleson. Academic Press. p.588. ISBN0-12-352651-5.
Müller, Ulrich; Bubenheim, Wilfried (26 August 1999). "Synthese und Kristallstrukturen von (NEt4)2[TeS3], (NEt4)2[Te(S5)(S7)] und (NEt4)4[Te(S5)2][Te(S7)2]" [Synthesis and crystal structure of (NEt4)2[TeS3], (NEt4)2[Te(S5)(S7)] and (NEt4)4[Te(S5)2][Te(S7)2]]. Zeitschrift für anorganische und allgemeine Chemie (in German). Wiley. 625 (9): 1522–1526. doi:10.1002/(SICI)1521-3749(199909)625:9<1522::AID-ZAAC1522>3.0.CO;2-D.
Bubenheim, Wilfried; Frenzen, Gerlinde; Müller, Ulrich (June 1994). "Synthese und Kristallstrukturen von (PPh4)2[TeS3]·2CH3CN und (PPh4)2[Te(S5)2]" [Synthesis and crystal structure of (PPh4)2[TeS3]·2CH3CN and (PPh4)2[Te(S5)2]]. Zeitschrift für anorganische und allgemeine Chemie (in German). Wiley. 620 (6): 1046–1050. doi:10.1002/zaac.19946200617.
↑ Kysliak, Oleksandr; Beck, Johannes (2013). "Chalcogenidotellurates(IV) (TeS3)2– and (TeSe3)2– by Low-Temperature Solvothermal Synthesis from Liquid Ammonia and Methylamine". European Journal of Inorganic Chemistry. Wernheim: Wiley-VCH. 2013: 124–133. doi:10.1002/ejic.201200927.
↑ McCarthy, TimothyJ.; Xiang Zhang; Kanatzidis, MercouriG. (June 1, 1993). "Synthesis of cesium copper sulfide CsCuS6, and Cs6Cu2(TeS3)2(S6)2 in molten cesium sulfide telluride, Cs2SxTey, salts: Novel compounds containing polychalcogenide ligands". Inorg. Chem. American Chemical Society. 32 (13): 2944–2948. doi:10.1021/ic00065a024.{{cite journal}}: CS1 maint: date and year (link)
Duck-Young Chung; Song-Ping Huang; Kang-Woo Kim; Kanatzidis, MercouriG. (August 1, 1995). "Discrete Complexes Incorporating Heteropolychalcogenide Ligands: Ring and Cage Structures in [Au2(TeS3)2]2-, [Ag2Te(TeS3)2]2-, and [Ag2Te(TeSe3)2]2-". Inorg. Chem. American Chemical Society. 34 (17): 4292–4293. doi:10.1021/ic00121a003.{{cite journal}}: CS1 maint: date and year (link)
Xiang Zhang; Kanatzidis, MercouriG. (March 1, 1994). "The Thiotellurites A2Mn(TeS3)2 (A = Cs, Rb): New Layered Solids Based on the Pyramidal TeS2- 3 Building Unit". Inorg. Chem. American Chemical Society. 33 (6): 1238–1240. doi:10.1021/ic00084a046.{{cite journal}}: CS1 maint: date and year (link)
↑ Babo, Jean-Marie; Wolff, KlausK.; Schleid, Thomas (2013). "Two New Cesium Thiotellurates: Cs2[TeS2] and Cs2[TeS3]". Z. Anorg. Allg. Chem. Wernheim: Wiley-VCH. 639 (15): 2875–2881. doi:10.1002/zaac.201300402.
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