Thallium halides

Short description: Class of elements

The thallium halides include monohalides TlX, where thallium has oxidation state +1, trihalides TlX
3, where thallium generally has oxidation state +3, and some intermediate halides containing thallium with mixed +1 and +3 oxidation states. X is a halogen. These salts 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 zinc sulfide optics are generally only usable to 650 cm−1 (15 μm).

## Contents

* 1 Monohalides
* 2 Thallium(I) mixed halides
* 3 Trihalides
* 3.1 Thallium(III) fluoride
* 3.2 Thallium(III) chloride
* 3.3 Thallium(III) bromide
* 3.4 Thallium(I) triiodide
* 4 Mixed-valence halides
* 5 Halide complexes
* 6 References
* 7 Further information

## Monohalides

Thallium(I) iodide has the CsCl crystal structure.

The monohalides, also known as thallous halides, 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 melting point 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, melting point 430 °C. The crystal structure is the same as CsCl.
Thallium(I) bromide
TlBr is a light sensitive, pale yellow crystalline solid, melting point 460 °C. The crystal structure is the same as CsCl.

Thallium(I) iodide
At room temperature, TlI is a yellow crystalline solid, melting point 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

File:6 KRS5 Tallium Bromide Iodide ingots Crystaltechno.jpgThallium bromide iodide ingots

Thallium bromoiodide or thallium bromide iodide (TlBr

1-x) and thallium bromochloride or thallium bromide chloride (TlBr
xCl
1-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 TlBr
0.4I
0.6 and TlBr
0.3Cl
0.7. 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, also known as thallic halides, 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 solid, mp 550 °C. Its structure is the same as YF
3 and β-BiF
3: 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

TlCl
3 has a distorted chromium(III) chloride structure like AlCl
3 and InCl
3. It can be prepared] by treating TlCl with Cl
2 gas.[9] Crystallization from water gives the tetrahydrate. Solid TlCl
3 decomposes at 40 °C, losing chlorine to give TlCl.

### Thallium(III) bromide

TlBr
3 can be prepared] by treating TlBr with Br
2 gas.[10] Crystallization from water gives the tetrahydrate. Solid TlBr
3 decomposes at 40 °C, losing bromine to give TlBr.[11]

### Thallium(I) triiodide

TlI
3 is a black crystalline solid prepared from TlI and I
2 in aqueous HI. It does not contain thallium(III), but has the same structure as CsI
3 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−

TlCl

This is formulated as TlI
TlIII

2Cl

This yellow compound is formulated TlI

3TlIII

6.[12]

2Br

This compound is similar to Tl
2Cl
3 and is formulated TlI

3TlIII

6[13]

TlBr

This pale brown solid is formulated TlI
TlIII

This compound has been reported as an intermediate in the synthesis of TlI
3 from TlI and I
2. The structure is not known.

## Halide complexes

Thallium(I) complexes
Thallium(I) can form complexes of the type (TlX
3)2− and (TlX
4)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 NaTlF
4 and Na
3TlF
6 do not contain discrete tetrahedral and octahedral anions. The structure of NaTlF
4 is the same as fluorite (CaF2) with NaI
and TlIII
atoms occupying the 8 coordinate CaII
sites. Na3TlF6 has the same structure as cryolite, Na
3AlF
6. 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 Tl
2Cl4−
10, long chain anions where TlIII
is 6 coordinate and the octahedral units are linked by bridging chlorine atoms, or mixed salts of TlIII

4 and TlIII

6.[14]

The ion Tl
2Cl3−
9, where thallium atoms are octahedrally coordinated with three bridging chlorine atoms, has been identified in the caesium salt, Cs
3Tl
2Cl

Thallium(III) bromide complexes
Salts of TlIII
Br−
4 and TlIII
Br3−
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−
.[15]

Thallium(III) iodide complexes
Salts of TlIII

4 are known. The TlIII
anion is stable even though the triiodide is a thallium(I) compound.

## 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" (in de). Angewandte Chemie (Wiley) 113 (24): 4760–4765. doi:10.1002/1521-3757(20011217)113:24<4760::aid-ange4760>3.0.co;2-6. ISSN 0044-8249. Bibcode: 2001AngCh.113.4760H.
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" (in en). Chemical Science 8 (6): 4602–4611. doi:10.1039/C7SC01219E. 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. https://docs.google.com/viewer?a=v&q=cache:NsfLFcXY8OQJ:www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0008948+&hl=en&gl=nz&pid=bl&srcid=ADGEESiGn5WoJc2xFvblN62oU19Sb_DPH8xnbL40R2liaoPVYG5QUEHebV_2rSjFEchjQC41LbtYT6eKeX1xrM23nRim4vcLiVFhc7y5IW52zmgixui72dOtSH-ppKEwBlCME2T-xz-P&sig=AHIEtbSwEWXnARSOjawhenrSc3QLPk4JlA.
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. ↑ E. Dönges (1963). "Thallium(IIl) ChlorideiI". in G. Brauer. Handbook of Preparative Inorganic Chemistry, 2nd Ed.. 2. NY, NY: Academic Press. pp. 890.
10. ↑ E. Dönges (1963). "Thallium(IIl) ChlorideiI". in G. Brauer. Handbook of Preparative Inorganic Chemistry, 2nd Ed.. 2. NY, NY: Academic Press. pp. 890.
11. ↑ 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.
12. ↑ 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.
13. ↑ Ackermann, Rupprecht; Hirschle, Christian; Rotter, Heinz W.; Thiele, Gerhard (2002). "Mixed-Valence Thallium(I, III) Bromides The Crystal Structure of α—Tl2Br3" (in de). Zeitschrift für anorganische und allgemeine Chemie (Wiley) 628 (12): 2675–2682. doi:10.1002/1521-3749(200212)628:12<2675::aid-zaac2675>3.0.co;2-4. ISSN 0044-2313.
14. ↑ 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.
15. ↑ 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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* t
* e

Thallium compounds

Thallium(I)|

* TlN3
* TlOH
* TlI
* TlBr
* Tl2CO3
* TlCl
* TlF
* Tl2O
* Tl2SO4
* Tl2S
* Tl2Te
* TlI3
* TBCCO

| Organothallium(I)|

* Tl(C2H3O2)3
* Tl2C3H2O4
* TlC5H5

|

Thallium(III)|

* TlH3
* Tl(OH)3
* Tl2O3
* Tl(NO3)3

* v
* t
* e

Fluorine compounds

| HF |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | He

|
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|
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LiF | BeF2 |  |  |  |  |  |  |  |  |  |  | BF3
B2F4 | CF4 | NF3 | OF2 | F− | Ne
NaF | MgF2 |  |  |  |  |  |  |  |  |  |  | AlF3 | SiF4 | PF3
PF5 | SF2
SF4
SF6 | ClF
ClF3
ClF5 | Ar
KF | CaF2 | ScF3 | TiF3
TiF4 | VF3
VF4
VF5 | CrF2
CrF3
CrF4
CrF5 | MnF2
MnF3 | FeF2
FeF3 | CoF2
CoF3 | NiF2 | CuF
CuF2 | ZnF2 | GaF3 | GeF4 | AsF3
AsF5 | SeF4
SeF6 | BrF3
BrF5 | KrF2
RbF | SrF2 | YF3 | ZrF4 | NbF4
NbF5 | MoF5
MoF6 | TcF6 | RuF3
RuF4
RuF5
RuF6 | RhF6 | PdF2 | AgF
AgF2
Ag2F | CdF2 | InF3 | SnF2
SnF4 | SbF3
SbF5 | TeF4 | IF
IF3
IF5
IF7 | XeF2
XeF4
XeF6
CsF | BaF2 | *  | HfF4 | TaF5 | WF4
WF6 | ReF4
ReF5
ReF6
ReF7 | OsF4
OsF5
OsF6 | IrF3
IrF5
IrF6 | PtF4
PtF6 | AuF3
Au2F10
AuF5·F2
| HgF2
Hg2F2 | TlF
TlF3 | PbF2
PbF4 | BiF3
BiF5 | Po | At | RnF2
Fr | Ra | **  | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Nh | Fl | Mc | Lv | Ts | Og
|  | ↓ |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
| * | LaF3 | CeF3 | Pr | NdF3 | PmF3 | SmF3
| Eu | Gd | Tb | DyF3 | Ho | Er | Tm | YbF3
| Lu |
| ** | AcF3 | ThF4 | Pa | UF3
UF4
UF5
UF6 | NpF3
NpF4
NpF5
NpF6
| PuF3
PuF4
PuF5
PuF6 | AmF3
AmF4 | CmF3 | Bk | Cf | Es | Fm | Md | No | Lr |

Other|

* AgBF4
* AgPF6
* Cs2AlF5
* K3AlF6
* Na3AlF6
* KAsF6
* LiAsF6
* NaAsF6
* HBF4
* KBF4
* LiBF4
* NaBF4
* RbBF4
* Ba(BF4)2
* Ni(BF4)2
* Pb(BF4)2
* Sn(BF4)2
* BaClF
* BaSiF6
* BaGeF6
* BrOF3
* BrO2F
* CBrF3
* CBr2F2
* CBr3F
* CClF3
* CCl2F2
* CCl3F
* CFN
* CF2O
* CF3I
* CHF3
* CH2F2
* CH3F
* C2Cl3F3
* C2H3F
* C6H5F
* C7H5F3
* C15F33N
* ClFO2
* CrFO4
* CrF2O2
* CsBF4
* NH4F
* FNO
* FNO2
* FNO3
* KHF2
* NaHF2
* ThOF2
* NH5F2
* (NH4)2SiF6
* F2OS
* F3OP
* PSF3
* HPF6
* HSbF6
* NH4PF6
* KPF6
* KSbF6
* LiPF6
* NaPF6
* NaSbF6
* Na2SiF6
* Na2TiF6
* Na2ZrF6
* TlPF6
* IOF3
* K2NbF7
* K2TaF7
* IO3F
* UO2F2

Chemical formulas

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