Thallium halides

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The thallium halides include monohalides, where thallium has oxidation state +1, trihalides in which thallium generally has oxidation state +3, and some intermediate halides containing thallium with mixed +1 and +3 oxidation states. These materials find use in specialized optical settings, such as focusing elements in research spectrophotometers. Compared to the more common zinc selenide-based optics, materials such as thallium bromoiodide enable transmission at longer wavelengths. In the infrared, this allows for measurements as low as 350 cm−1 (28 μm), whereas zinc selenide is opaque by 21.5 μm, and ZnSe optics are generally only usable to 650 cm−1 (15 μm).

Contents

Monohalides

Thallium(I) iodide has the CsCl crystal structure. Thallium-iodide-3D-vdW.png
Thallium(I) iodide has the CsCl crystal structure.

The monohalides all contain thallium with oxidation state +1. Parallels can be drawn between the thallium(I) halides and their corresponding silver salts; for example, thallium(I) chloride and bromide are light-sensitive, and thallium(I) fluoride is more soluble in water than the chloride and bromide.

Thallium(I) fluoride
TlF is a white crystalline solid, with a mp of 322 °C. It is readily soluble in water unlike the other Tl(I) halides. The normal room-temperature form has a similar structure to α-PbO which has a distorted rock salt structure with essentially five coordinate thallium, the sixth fluoride ion is at 370 pm. At 62 °C it transforms to a tetragonal structure. This structure is unchanged up to pressure of 40 GPa. [1]
The room temperature structure has been explained in terms of interaction between Tl 6s and the F 2p states producing strongly antibonding Tl-F states. The structure distorts to minimise these unfavourable covalent interactions. [2]
Thallium(I) chloride
TlCl is a light sensitive, white crystalline solid, mp 430 °C. The crystal structure is the same as CsCl.
Thallium(I) bromide
TlBr is a light sensitive, pale yellow crystalline solid, mp 460 °C. The crystal structure is the same as CsCl.
Thallium(I) iodide
At room temperature, TlI is a yellow crystalline solid, mp 442 °C. The crystal structure is a distorted rock salt structure known as the β-TlI structure. At higher temperatures the colour changes to red with a structure the same as CsCl. [3]

Thallium(I) mixed halides

Thallium bromide iodide ingots 6 KRS5 Tallium Bromide Iodide ingots Crystaltechno.jpg
Thallium bromide iodide ingots

Thallium bromoiodide / thallium bromide iodide (TlBrxI1−x) and thallium bromochloride / thallium bromide chloride (TlBrxCl1−x) are mixed salts of thallium(I) that are used in spectroscopy as an optical material for transmission, refraction, and focusing of infrared radiation. The materials were first grown by R. Koops in the laboratory of Olexander Smakula at the Carl Zeiss Optical Works, Jena in 1941. [4] [5] The red bromoiodide was coded KRS-5 [6] and the colourless bromochloride, KRS-6 [7] and this is how they are commonly known. The KRS prefix is an abbreviation of "Kristalle aus dem Schmelz-fluss", (crystals from the melt). The compositions of KRS-5 and KRS-6 approximate to TlBr0.4I0.6 and TlBr0.3Cl0.7. KRS-5 is the most commonly used, its properties of being relatively insoluble in water and non-hygroscopic, make it an alternative to KBr, CsI, and AgCl. [8]

Trihalides

The thallium trihalides are less stable than their corresponding aluminium, gallium, and indium counterparts and chemically quite distinct. The triiodide does not contain thallium with oxidation state +3 but is a thallium(I) compound and contains the linear I−3 ion.

Thallium(III) fluoride
TlF3 is a white crystalline solid, mp 550 °C. The crystal structure is the same as YF3 and β-BiF3. In this the thallium atom is 9 coordinate (tricapped trigonal prismatic). It can be synthesised by fluoridation of the oxide, Tl2O3, with F2, BrF3, or SF4 at 300 °C.
Thallium(III) chloride
TlCl3 has a distorted Cr(III) chloride structure like AlCl3 and InCl3. Solid TlCl3 is unstable and disproportionates at 40 °C, losing chlorine to give TlCl . It can be prepared in CH3CN by treating a solution of TlCl with Cl2 gas.
Thallium(III) bromide
This unstable compound disproportionates at less than 40 °C to TlBr and Br2. It can be prepared in CH3CN by treating a solution of TlBr with Br2 gas. In water the tetrahydrate complex can be prepared by adding bromine to a stirred suspension of TlBr. [9]
Thallium(I) triiodide
TlI3 is a black crystalline solid prepared from TlI and I2 in aqueous HI. It does not contain thallium(III), but has the same structure as CsI3 containing the linear I−3 ion.

Mixed-valence halides

As a group, these are not well characterised. They contain both Tl(I) and Tl(III), where the thallium(III) atom is present as complex anions, e.g. TlCl−4.

TlCl2
This is formulated as TlITlIIICl4.
Tl2Cl3
This yellow compound is formulated TlI3TlIIICl6. [10]
Tl2Br3
This compound is similar to Tl2Cl3 and is formulated TlI3TlIIIBr6 [11]
TlBr2
This pale brown solid is formulated TlITlIIIBr4
Tl3I4
This compound has been reported as an intermediate in the synthesis of TlI3 from TlI and I2. The structure is not known.

Halide complexes

Thallium(I) complexes
Thallium(I) can form complexes of the type (TlX3)2− and (TlX4)3− both in solution and when thallium(I) halides are incorporated into alkali metal halides. These doped alkali metal halides have new absorption and emission nbands and are used as phosphors in scintillation radiation detectors.
Thallium(III) fluoride complexes
The salts NaTlF4 and Na3TlF6 do not contain discrete tetrahedral and octahedral anions. The structure of NaTlF4 is the same as fluorite (CaF2) with NaI and TlIII atoms occupying the 8 coordinate CaII sites. Na3TlF6 has the same structure as cryolite, Na3AlF6. In this the thallium atoms are octahedrally coordinated. Both compounds are usually considered to be mixed salts of Na+ and Tl3+.
Thallium(III) chloride complexes
Salts of tetrahedral TlCl−4 and octahedral TlCl3−6 are known with various cations.
Salts containing TlCl2−5 with a square pyramidal structure are known. Some salts that nominally contain TlCl2−5 actually contain the dimeric anion Tl2Cl4−10, long chain anions where TlIII is 6 coordinate and the octahedral units are linked by bridging chlorine atoms, or mixed salts of TlIIICl4 and TlIIICl6. [12]
The ion Tl2Cl3−9, where thallium atoms are octahedrally coordinated with three bridging chlorine atoms, has been identified in the caesium salt, Cs3Tl2Cl9.
Thallium(III) bromide complexes
Salts of TlIIIBr−4 and TlIIIBr3−6 are known with various cations.
The TlBr2−5 anion has been characterised in a number of salts and is trigonal bipyramidal. Some other salts that nominally contain TlBr2−5 are mixed salts containing TlBr−4 and Br−. [13]
Thallium(III) iodide complexes
Salts of TlIIII−4 are known. The TlIII anion is stable even though the triiodide is a thallium(I) compound.

Related Research Articles

In chemistry, a halide is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative than the halogen, to make a fluoride, chloride, bromide, iodide, astatide, or theoretically tennesside compound. The alkali metals combine directly with halogens under appropriate conditions forming halides of the general formula, MX. Many salts are halides; the hal- syllable in halide and halite reflects this correlation. All Group 1 metals form halides that are white solids at room temperature.

<span class="mw-page-title-main">Silver bromide</span> Chemical compound

Silver bromide (AgBr) is a soft, pale-yellow, water-insoluble salt well known for its unusual sensitivity to light. This property has allowed silver halides to become the basis of modern photographic materials. AgBr is widely used in photographic films and is believed by some to have been used for making the Shroud of Turin. The salt can be found naturally as the mineral bromargyrite.

In chemistry, water(s) of crystallization or water(s) of hydration are water molecules that are present inside crystals. Water is often incorporated in the formation of crystals from aqueous solutions. In some contexts, water of crystallization is the total mass of water in a substance at a given temperature and is mostly present in a definite (stoichiometric) ratio. Classically, "water of crystallization" refers to water that is found in the crystalline framework of a metal complex or a salt, which is not directly bonded to the metal cation.

<span class="mw-page-title-main">Tetrafluoroborate</span> Anion

Tetrafluoroborate is the anion BF−
4. This tetrahedral species is isoelectronic with tetrafluoroberyllate (BeF2−
4), tetrafluoromethane (CF4), and tetrafluoroammonium (NF+
4) and is valence isoelectronic with many stable and important species including the perchlorate anion, ClO−
4, which is used in similar ways in the laboratory. It arises by the reaction of fluoride salts with the Lewis acid BF3, treatment of tetrafluoroboric acid with base, or by treatment of boric acid with hydrofluoric acid.

<span class="mw-page-title-main">Vanadium(III) bromide</span> Chemical compound

Vanadium(III) bromide, also known as vanadium tribromide, describes the inorganic compounds with the formula VBr3 and its hydrates. The anhydrous material is a green-black solid. In terms of its structure, the compound is polymeric with octahedral vanadium(III) surrounded by six bromide ligands.

<span class="mw-page-title-main">Indium(III) chloride</span> Chemical compound

Indium(III) chloride is the chemical compound with the formula InCl3 which forms a tetrahydrate. This salt is a white, flaky solid with applications in organic synthesis as a Lewis acid. It is also the most available soluble derivative of indium. This is one of three known indium chlorides.

<span class="mw-page-title-main">Gallium(III) bromide</span> Chemical compound

Gallium(III) bromide (GaBr3) is a chemical compound, and one of four gallium trihalides.

Bromine compounds are compounds containing the element bromine (Br). These compounds usually form the -1, +1, +3 and +5 oxidation states. Bromine is intermediate in reactivity between chlorine and iodine, and is one of the most reactive elements. Bond energies to bromine tend to be lower than those to chlorine but higher than those to iodine, and bromine is a weaker oxidising agent than chlorine but a stronger one than iodine. This can be seen from the standard electrode potentials of the X2/X− couples (F, +2.866 V; Cl, +1.395 V; Br, +1.087 V; I, +0.615 V; At, approximately +0.3 V). Bromination often leads to higher oxidation states than iodination but lower or equal oxidation states to chlorination. Bromine tends to react with compounds including M–M, M–H, or M–C bonds to form M–Br bonds.

There are three sets of Indium halides, the trihalides, the monohalides, and several intermediate halides. In the monohalides the oxidation state of indium is +1 and their proper names are indium(I) fluoride, indium(I) chloride, indium(I) bromide and indium(I) iodide.

There are three sets of gallium halides, the trihalides where gallium has oxidation state +3, the intermediate halides containing gallium in oxidation states +1, +2 and +3 and some unstable monohalides, where gallium has oxidation state +1.

<span class="mw-page-title-main">Berkelium compounds</span> Any chemical compound having at least one berkelium atom

Berkelium forms a number of chemical compounds, where it normally exists in an oxidation state of +3 or +4, and behaves similarly to its lanthanide analogue, terbium. Like all actinides, berkelium easily dissolves in various aqueous inorganic acids, liberating gaseous hydrogen and converting into the trivalent oxidation state. This trivalent state is the most stable, especially in aqueous solutions, but tetravalent berkelium compounds are also known. The existence of divalent berkelium salts is uncertain and has only been reported in mixed lanthanum chloride-strontium chloride melts. Aqueous solutions of Bk3+ ions are green in most acids. The color of the Bk4+ ions is yellow in hydrochloric acid and orange-yellow in sulfuric acid. Berkelium does not react rapidly with oxygen at room temperature, possibly due to the formation of a protective oxide surface layer; however, it reacts with molten metals, hydrogen, halogens, chalcogens and pnictogens to form various binary compounds. Berkelium can also form several organometallic compounds.

<span class="mw-page-title-main">Metal halides</span>

Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, such as palladium chloride.

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.

Polyhalogen ions are a group of polyatomic cations and anions containing halogens only. The ions can be classified into two classes, isopolyhalogen ions which contain one type of halogen only, and heteropolyhalogen ions with more than one type of halogen.

<span class="mw-page-title-main">Californium(III) bromide</span> Chemical compound

Californium(III) bromide is an inorganic compound, a salt with a chemical formula CfBr3. Like in californium oxide (Cf2O3) and other californium halides, including californium(III) fluoride (CfF3), californium(III) chloride, and californium(III) iodide (CfI3), the californium atom has an oxidation state of +3.

Antimonide bromides or bromide antimonides are compounds containing anions composed of bromide (Br−) and antimonide (Sb3−). They can be considered as mixed anion compounds. They are in the category of pnictidehalides. Related compounds include the antimonide chlorides, antimonide iodides, arsenide chlorides, arsenide bromides, arsenide iodides, phosphide chlorides, phosphide bromides, and phosphide iodides. The bromoantimonates have antimony in positive oxidation states.

Einsteinium compounds are compounds that contain the element einsteinium (Es). These compounds largely have einsteinium in the +3 oxidation state, or in some cases in the +2 and +4 oxidation states. Although einsteinium is relatively stable, with half-lives ranging from 20 days upwards, these compounds have not been studied in great detail.

<span class="mw-page-title-main">Zirconium(III) bromide</span> Chemical compound

Zirconium(III) bromide is an inorganic compound with the formula ZrBr3.

Protactinium compounds are compounds containing the element protactinium. These compounds usually have protactinium in the +5 oxidation state, although these compounds can also exist in the +2, +3 and +4 oxidation states.

References

  1. ↑ Häussermann, Ulrich; Berastegui, Pedro; Carlson, Stefan; Haines, Julien; Léger, Jean-Michel (2001-12-17). "TlF and PbO under High Pressure: Unexpected Persistence of the Stereochemically Active Electron Pair". Angewandte Chemie (in German). Wiley. 113 (24): 4760–4765. doi:10.1002/1521-3757(20011217)113:24<4760::aid-ange4760>3.0.co;2-6. ISSN   0044-8249.
  2. ↑ Mudring, Anja Verena (2007). "Thallium Halides – New Aspects of the Stereochemical Activity of Electron Lone Pairs of Heavier Main Group Elements". European Journal of Inorganic Chemistry. Wiley. 2007 (6): 882–890. doi:10.1002/ejic.200600975. ISSN   1434-1948.
  3. ↑ Mir, Wasim J.; Warankar, Avinash; Acharya, Ashutosh; Das, Shyamashis; Mandal, Pankaj; Nag, Angshuman (2017). "Colloidal thallium halide nanocrystals with reasonable luminescence, carrier mobility and diffusion length". Chemical Science. 8 (6): 4602–4611. doi:10.1039/C7SC01219E. PMC   5618336 . PMID   28970882.
  4. ↑ Koops, R. (1948). "Optical structural subjects from binary mixed crystals". Optik (3): 298–304.
  5. ↑ Smakula, A.; Kalnajs, J.; Sils, V. (March 1953). "Inhomogeneity of Thallium Halide Mixed Crystals and Its Elimination". Laboratory for Insulation Research Technical Report 67. Massachusetts Institute of Technology . Retrieved October 17, 2012.
  6. ↑ Crystran Data for KRS5 https://www.crystran.co.uk/optical-materials/krs5-thallium-bromo-iodide-tlbr-tli
  7. ↑ Crystran Data for KRS6 https://www.crystran.co.uk/optical-materials/krs6-thallium-bromo-chloride-tlbr-tlcl
  8. ↑ Frank Twyman (1988) Prism and Lens Making: A Textbook for Optical Glassworkers CRC Press ISBN   0-85274-150-2, page 170
  9. ↑ Glaser, Julius; Fjellvåg, Helmer; Kjekshus, Arne; Andresen, Arne F.; Sokolov, V. B.; Spiridonov, V. P.; Strand, T. G. (1979). "Crystal and Molecular Structure of Thallium(III) Bromide Tetrahydrate and Thallium(III) Chloride Tetrahydrate, a Redetermination". Acta Chemica Scandinavica. Danish Chemical Society. 33A: 789–794. doi: 10.3891/acta.chem.scand.33a-0789 . ISSN   0904-213X.
  10. ↑ Böhme, Reinhild; Rath, Jörg; Grunwald, Bernd; Thiele, Gerhard (1980-11-01). "Über zwei Modifikationen von "Tl2Cl3"-valenzgemischten Thallium(I)-hexahalogenothallaten(III) Tl3 [TlCl6] / On Two Modifications of "Tl2Cl3"-Mixed Valence Thallium(I)-hexahalogenothallates(III)". Zeitschrift für Naturforschung B. Walter de Gruyter GmbH. 35 (11): 1366–1372. doi: 10.1515/znb-1980-1108 . ISSN   1865-7117.
  11. ↑ Ackermann, Rupprecht; Hirschle, Christian; Rotter, Heinz W.; Thiele, Gerhard (2002). "Mixed-Valence Thallium(I, III) Bromides The Crystal Structure of α—Tl2Br3". Zeitschrift für anorganische und allgemeine Chemie (in German). Wiley. 628 (12): 2675–2682. doi:10.1002/1521-3749(200212)628:12<2675::aid-zaac2675>3.0.co;2-4. ISSN   0044-2313.
  12. ↑ James, Margaret Ann; Clyburne, Jason A.C.; Linden, Anthony; James, Bruce D.; Liesegang, John; Zuzich, Vilma (1996-08-01). "Structural diversity in thallium chemistry: structures of four chlorothallate(III) salts including a novel compound containing three geometrically different anions". Canadian Journal of Chemistry. Canadian Science Publishing. 74 (8): 1490–1502. doi: 10.1139/v96-166 . ISSN   0008-4042.
  13. ↑ Linden, Anthony; Nugent, Kerry W.; Petridis, Alexander; James, Bruce D. (1999). "Structural diversity in thallium chemistry". Inorganica Chimica Acta. Elsevier BV. 285 (1): 122–128. doi:10.1016/s0020-1693(98)00339-9. ISSN   0020-1693.

Further information

  1. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN   978-0-08-037941-8.
  2. Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN   0-471-19957-5
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