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Germanium tetrachloride
Germanium tetrachloride - structural formula	Germanium tetrachloride - space-filling model
Names
	IUPAC names Germanium tetrachloride; Tetrachlorogermane; Tetrachloridogermanium
	Other names Germanium(IV) chloride; Neutral germanium chloride (1:4)
Identifiers
CAS Number	10038-98-9 ;
3D model (JSmol)	Interactive image;
ChemSpider	59611 ;
ECHA InfoCard	100.030.093
PubChem CID	66226;
RTECS number	LY5220000;
UNII	YSV1R803C0 ;
CompTox Dashboard (EPA)	DTXSID1044350 ;
	InChI InChI=1S/Cl4Ge/c1-5(2,3)4 Key: IEXRMSFAVATTJX-UHFFFAOYSA-N ; InChI=1S/Cl4Ge/c1-5(2,3)4 Key: IEXRMSFAVATTJX-UHFFFAOYSA-N;
	SMILES Cl[Ge](Cl)(Cl)Cl;
Properties
Chemical formula	GeCl4
Molar mass	214.40 g/mol
Appearance	Colourless liquid
Density	1.879 g/cm3 (20 °C) ; 1.844 g/cm3 (30 °C)
Melting point	−49.5 °C (−57.1 °F; 223.7 K)
Boiling point	86.5 °C (187.7 °F; 359.6 K)
Solubility in water	Soluble, hydrolyses
Solubility	Soluble in ether, benzene, chloroform, CCl4 ; Very soluble in HCl, dilute H2SO4
Magnetic susceptibility (χ)	−72.0·10−6 cm3/mol
Refractive index (nD)	1.464
Structure
Molecular shape	tetrahedral
Thermochemistry
Std molar; entropy (S⦵298)	245.6 J·mol−1·K−1
Std enthalpy of; formation (ΔfH⦵298)	−531.8 kJ·mol−1
Gibbs free energy (ΔfG⦵)	−462.7 kJ·mol−1
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Reacts slowly with water to form HCl and GeO2, corrosive, lachrymator
NFPA 704 (fire diamond)	3 0 2 W
Flash point	Non-flammable
Safety data sheet (SDS)	"External MSDS"
Related compounds
Other anions	Germanium tetrafluoride; Germanium tetrabromide; Germanium tetraiodide
Other cations	Carbon tetrachloride; Silicon tetrachloride; Tin(IV) chloride; Lead(IV) chloride
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Germanium tetrachloride is a colourless, fuming liquid^[4] with a peculiar, acidic odour. It is used as an intermediate in the production of purified germanium metal. In recent years, GeCl₄ usage has increased substantially due to its use as a reagent for fiber optic production.

Production

Most commercial production of germanium is from treating flue-dusts of zinc- and copper-ore smelters, although a significant source is also found in the ash from the combustion of certain types of coal called vitrain. Germanium tetrachloride is an intermediate for the purification of germanium metal or its oxide, GeO₂.^[5]

Germanium tetrachloride can be generated directly from GeO₂ (germanium dioxide) by dissolution of the oxide in concentrated hydrochloric acid. The resulting mixture is fractionally distilled to purify and separate the germanium tetrachloride from other products and impurities.^[6] The GeCl₄ can be rehydrolysed with deionized water to produce pure GeO₂, which is then reduced under hydrogen to produce germanium metal.^[5]^[6]

Production of GeO₂, however, is dependent on the oxidized form of germanium extracted from the ore. Copper-lead-sulfide and zinc-sulfide ores will produce GeS₂, which is subsequently oxidized to GeO₂ with an oxidizer such as sodium chlorate. Zinc-ores are roasted and sintered and can produce the GeO₂ directly. The oxide is then processed as discussed above.^[5]

The classic synthesis from chlorine and germanium metal at elevated temperatures is also possible.^[7]^[1] Additionally, a chlorine free activation of germanium has been developed, giving a less energy intensive and more environmentally friendly alternative synthesis for germanium precursors.

Application

Germanium tetrachloride is used almost exclusively as an intermediate for several optical processes. GeCl₄ can be directly hydrolysed to GeO₂, an oxide glass with several unique properties and applications, described below and in linked articles:

Fiber optics

A notable derivative of GeCl₄ is germanium dioxide. In the manufacture of optical fibers, silicon tetrachloride, SiCl₄, and germanium tetrachloride, GeCl₄, are introduced with oxygen into a hollow glass preform, which is carefully heated to allow for oxidation of the reagents to their respective oxides and formation of a glass mixture. The GeO₂ has a high index of refraction, so by varying the flow rate of germanium tetrachloride the overall index of refraction of the optical fiber can be specifically controlled. The GeO₂ is about 4% by weight of the glass.^[5]

References

^ ^a ^b P.W. Schenk (1963). "Germanium(IV) Chloride". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 1. NY, NY: Academic Press. pp. 715–716.
^ Merz, K.; Driess, M. (2002). "Germanium(IV) chloride at 193 K". Acta Crystallogr. C. 58 (Pt 7): i101–i102. doi:10.1107/S0108270102010351. PMID 12094027.
^ CRC handbook of chemistry and physics : a ready-reference book of chemical and physical data. William M. Haynes, David R. Lide, Thomas J. Bruno (2016-2017, 97th ed.). Boca Raton, Florida. 2016. ISBN 978-1-4987-5428-6. OCLC 930681942.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 377. ISBN 978-0-08-037941-8.
^ ^a ^b ^c ^d "Germanium" Mineral Commodity Profile, U.S. Geological Survey, 2005.
^ ^a ^b "The Elements" C. R. Hammond, David R. Lide, ed. CRC Handbook of Chemistry and Physics, Edition 85 (CRC Press, Boca Raton, Florida) (2004)
^ "GeCl4 synthesis". account.e.jimdo.com. Technische Universitä Ilmenau. Retrieved 2020-09-22.