Germane

Germanium tetrahydride
IUPAC name

Germane
Other names

Germanium tetrahydride
Germanomethane
Monogermane
Identifiers
CAS number 7782-65-2 Y
PubChem 23984
ChemSpider 22420 Y
UN number 2192
KEGG C15472 Y
ChEBI CHEBI:30443 Y
RTECS number LY4900000
Jmol-3D images Image 1
Properties
Molecular formula GeH4
Molar mass 76.62 g/mol1
Appearance Colorless gas
Density 3.3 kg/m3 gas
Melting point

−165 °C (108 K)
Boiling point

−88 °C (185 K)
Solubility in water low
Structure
Molecular shape Tetrahedral
Dipole moment O D
Hazards
MSDS ICSC 1244
EU Index Not listed
Main hazards Toxic, flammable
NFPA 704
4
4
3
Related compounds
Related compounds Methane
Silane
Stannane
Plumbane
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Germane is the chemical compound with the formula GeH4, 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.

Contents

Occurrence

Germane has been detected in the atmosphere of Jupiter.[1]

Synthesis

Many methods are known for the industrial manufacture of germane.[2] These processes can be categorized as:

The chemical reduction method involves reacting a germanium-containing compound such as elemental germanium, germanium tetrachloride, or germanium dioxide with a reducing agent such as sodium borohydride, potassium borohydride, lithium borohydride, lithium aluminium hydride, sodium aluminium hydride, lithium hydride, sodium hydride, or magnesium hydride. The reaction can be carried out in either aqueous or in an organic solvent. On laboratory scale, germane can be prepared by the reaction of Ge(IV) compounds with hydride reagents. A typical synthesis involved the reaction of Na2GeO3 with sodium borohydride.[3]

Na2GeO3 + NaBH4 + H2O → GeH4 + 2 NaOH + NaBO2

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.

Lastly, 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.

US Patent 4,668,502 discloses a process for manufacture of germane gas using germanium dioxide and sodium borohydride.

Reactions

In liquid ammonia GeH4 is ionised forming NH4+ and GeH3−.[4] With alkali metals in liquid ammonia GeH4 reacts to give white crystalline MGeH3 compounds. The potassium and rubidium compounds have the sodium chloride structure implying a free rotation of the GeH3− anion, the caesium compound, CsGeH3 in contrast has the distorted sodium chloride structure of TlI.[4]

Use in semiconductor industry

The gas decomposes near 600K 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.[5] 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.[6]

Safety

Germane is a highly flammable, potentially pyrophoric [7], and 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. [8] The LC50 for rats at 1 hour of exposure is 622 ppm. [9] Inhalation exposure may result in malaise, headache, dizziness, fainting, dyspnea, nausea, vomiting, kidney injury, and hemolytic effects. [10] [11] [12]

The US Department of Transportation hazard class is 2.3 Poisonous Gas.[13]

References

  1. ^ Kunde, V.; Hanel, R.; Maguire, W.; Gautier, D.; Baluteau, J. P.; Marten, A.; Chedin, A.; Husson, N.; Scott, N. (1982). "The tropospheric gas composition of Jupiter's north equatorial belt /NH3, PH3, CH3D, GeH4, H2O/ and the Jovian D/H isotopic ratio". Astrophysical J. 263: 443–467. Bibcode 1982ApJ...263..443K. doi:10.1086/160516. 
  2. ^ US Patent 7,087,102 (2006)
  3. ^ Girolami, G. S.; Rauchfuss, T. B. and Angelici, R. J., Synthesis and Technique in Inorganic Chemistry, University Science Books: Mill Valley, CA, 1999.
  4. ^ a b Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Oxford: Butterworth-Heinemann. ISBN 0080379419. 
  5. ^ 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. 
  6. ^ E. Woelk, D. V. Shenai-Khatkhate, R. L. DiCarlo, Jr., A. Amamchyan, M. B. Power, B. Lamare, G. Beaudoin, I. Sagnes (2006). "Designing Novel Organogermanium MOVPE Precursors for High-purity Germanium Films". Journal of Crystal Growth 287 (2): 684–687. Bibcode 2006JCrGr.287..684W. doi:10.1016/j.jcrysgro.2005.10.094. 
  7. ^ Brauer, 1963, Vol.1, 715
  8. ^ Praxair MSDS accessed Sep. 2011
  9. ^ NIOSH Germane Registry of Toxic Effects of Chemical Substances (RTECS)accessed Sep. 2011
  10. ^ Guskova, E.I. 1974. Toxicology of germanium tetrahydride. Gig Tr Prof Zabol. 2: 56-57.
  11. ^ US EPA Germane
  12. ^ Paneth, F. and Joachimoglu, G. 1924. The pharmacological characteristics of tin [IV] hydride (stannane) and germanium hydride. Berichte der Deutschen Chemischen Gesellschaft, 57: 1925-1930.
  13. ^ Praxair MSDS accessed Sep. 2011

External links