Germane

Germane
	Germanium, Ge Hydrogen, H
Names
	IUPAC name Germane
	Other names Germanium tetrahydride; Germanomethane; Monogermane
Identifiers
CAS Number	7782-65-2 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:30443 ;
ChemSpider	22420 ;
EC Number	231-961-6;
Gmelin Reference	587
KEGG	C15472 ;
PubChem CID	23984;
RTECS number	LY4900000;
UNII	619P6J82AE ;
UN number	2192
	InChI InChI=1S/GeH4/h1H4 Key: QUZPNFFHZPRKJD-UHFFFAOYSA-N ; InChI=1/GeH4/h1H4 Key: QUZPNFFHZPRKJD-UHFFFAOYAE;
	SMILES [H][Ge]([H])([H])[H];
Properties
Chemical formula	GeH4
Molar mass	76.62 g/mol
Appearance	Colorless gas
Odor	Pungent
Density	3.3 kg/m3
Melting point	−165 °C (−265 °F; 108 K)
Boiling point	−88 °C (−126 °F; 185 K)
Solubility in water	Low
Vapor pressure	>1 atm
Viscosity	17.21 μPa·s ; (theoretical estimate)
Structure
Molecular shape	Tetrahedral
Dipole moment	0 D
Hazards
Main hazards	Toxic, flammable, may ignite spontaneously in air
Safety data sheet	ICSC 1244
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H220, H280, H302, H330
GHS precautionary statements	P210, P260, P264, P270, P271, P284, P301+312, P304+340, P310, P320, P330, P377, P381, P403, P403+233, P405, P410+403, P501
NFPA 704 (fire diamond)	4 4 3
	NIOSH (US health exposure limits):
PEL (Permissible)	None
REL (Recommended)	TWA 0.2 ppm (0.6 mg/m3)
IDLH (Immediate danger)	N.D.
Related compounds
Related compounds	Methane; Silane; Stannane; Plumbane; Germyl
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references

Germane is the chemical compound with the formula Ge H₄, and the germanium analogue of methane. It is the simplest germanium hydride and one of the most useful compounds of germanium. Like the related compounds silane and methane, germane is tetrahedral. It burns in air to produce GeO₂ and water. Germane is a group 14 hydride.

Occurrence

Germane has been detected in the atmosphere of Jupiter.^[3]

Synthesis

Germane is typically prepared by reduction of germanium oxides, notably germanates, with hydride reagents such as sodium borohydride, potassium borohydride, lithium borohydride, lithium aluminium hydride, sodium aluminium hydride. The reaction with borohydrides is catalyzed by various acids and can be carried out in either aqueous or organic solvent. On laboratory scale, germane can be prepared by the reaction of Ge(IV) compounds with these hydride reagents.^[4]^[5] A typical synthesis involved the reaction of potassium germanate with sodium borohydride.^[6]

NaHGeO₃ + KBH₄ + H₂O → KGeH₃ + KB(OH)₄

KGeH₃ + HO₂CCH₃ → GeH₄ + KO₂CCH₃

Other methods for the synthesis of germane include electrochemical reduction and a plasma-based method.^[7] The electrochemical reduction method involves applying voltage to a germanium metal cathode immersed in an aqueous electrolyte solution and an anode counter-electrode composed of a metal such as molybdenum or cadmium. In this method, germane and hydrogen gases evolve from the cathode while the anode reacts to form solid molybdenum oxide or cadmium oxides. The plasma synthesis method involves bombarding germanium metal with hydrogen atoms (H) that are generated using a high frequency plasma source to produce germane and digermane.

Reactions

Germane is weakly acidic. In liquid ammonia GeH₄ is ionised forming NH₄⁺ and GeH₃⁻.^[8] With alkali metals in liquid ammonia GeH₄ reacts to give white crystalline MGeH₃ compounds. The potassium (potassium germyl or potassium trihydrogen germanide KGeH₃) and rubidium compounds (rubidium germyl or rubidium trihydrogen germanide RbGeH₃) have the sodium chloride structure implying a free rotation of the trihydrogen germanide anion GeH₃⁻, the caesium compound, caesium germyl or caesium trihydrogen germanide CsGeH₃ in contrast has the distorted sodium chloride structure of TlI.^[8]

Use in semiconductor industry

The gas decomposes near 600K (327°C; 620°F) to germanium and hydrogen. Because of its thermal lability, germane is used in the semiconductor industry for the epitaxial growth of germanium by MOVPE or chemical beam epitaxy.^[9] Organogermanium precursors (e.g. isobutylgermane, alkylgermanium trichlorides, and dimethylaminogermanium trichloride) have been examined as less hazardous liquid alternatives to germane for deposition of Ge-containing films by MOVPE.^[10]

Safety

Germane is a highly flammable, potentially pyrophoric,^[11] and a highly toxic gas. In 1970, the American Conference of Governmental Industrial Hygienists (ACGIH) published the latest changes and set the occupational exposure threshold limit value at 0.2 ppm for an 8-hour time weighted average.^[12] The LC50 for rats at 1 hour of exposure is 622 ppm.^[13] Inhalation or exposure may result in malaise, headache, dizziness, fainting, dyspnea, nausea, vomiting, kidney injury, and hemolytic effects.^[14]^[15]^[16]

The US Department of Transportation hazard class is 2.3 Poisonous Gas.^[12]

References

↑ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 NIOSH Pocket Guide to Chemical Hazards. "#0300". National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/npg/npgd0300.html.
↑ Yaws, Carl L. (1997), Handbook Of Viscosity: Volume 4: Inorganic Compounds And Elements, Gulf Professional Publishing, ISBN 978-0123958501
↑ Kunde, V.; Hanel, R.; Maguire, W.; Gautier, D.; Baluteau, J. P.; Marten, A.; Chedin, A.; Husson, N. et al. (1982). "The tropospheric gas composition of Jupiter's north equatorial belt (NH₃, PH₃, CH₃D, GeH₄, H₂O) and the Jovian D/H isotopic ratio". Astrophysical Journal 263: 443–467. doi:10.1086/160516. Bibcode: 1982ApJ...263..443K.
↑ W. L. Jolly "Preparation of the Volatile Hydrides of Groups IVA and VA by Means of Aqueous Hydroborate" Journal of the American Chemical Society 1961, volume 83, pp. 335-7.
↑ US Patent 4,668,502
↑ Girolami, G. S.; Rauchfuss, T. B.; Angelici, R. J. (1999). Synthesis and Technique in Inorganic Chemistry. Mill Valley, CA: University Science Books.
↑ US Patent 7,087,102 (2006)
↑ ^8.0 ^8.1 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
↑ Venkatasubramanian, R.; Pickett, R. T.; Timmons, M. L. (1989). "Epitaxy of germanium using germane in the presence of tetramethylgermanium". Journal of Applied Physics 66 (11): 5662–5664. doi:10.1063/1.343633. Bibcode: 1989JAP....66.5662V.
↑ Woelk, E.; Shenai-Khatkhate, D. V.; DiCarlo, R. L. Jr.; Amamchyan, A.; Power, M. B.; Lamare, B.; Beaudoin, G.; Sagnes, I. (2006). "Designing Novel Organogermanium MOVPE Precursors for High-purity Germanium Films". Journal of Crystal Growth 287 (2): 684–687. doi:10.1016/j.jcrysgro.2005.10.094. Bibcode: 2006JCrGr.287..684W.
↑ Brauer, 1963, Vol.1, 715
↑ ^12.0 ^12.1 Praxair MSDS accessed Sep. 2011
↑ NIOSH Germane Registry of Toxic Effects of Chemical Substances (RTECS)accessed Sep. 2011
↑ Gus'kova, E. I. (1974). "K toksikologii Gidrida Germaniia" (in Russian). Gigiena Truda I Professionalnye Zabolevaniia 18 (2): 56–57. PMID 4839911.
↑ US EPA Germane
↑ Paneth, F.; Joachimoglu, G. (1924). "Über die pharmakologischen Eigenschaften des Zinnwasserstoffs und Germaniumwasserstoffs" (in German). Berichte der Deutschen Chemischen Gesellschaft 57 (10): 1925–1930. doi:10.1002/cber.19240571027.