Group 14 hydride

Structure of methane, silane, germane, and stannane.

Group 14 hydrides are chemical compounds with a group 14 element directly bonded to hydrogen. The elements of group 14 are carbon, silicon, germanium, tin, and lead. This article focuses on parent compounds with the formula EHnx, where x can reflect neutral members or anions and cations.

Charge-neutral hydrides

Monohydrides

Monohydrides are rare for the group 14 elements. Methylidyne (CH) has been observed in the interstellar medium. With one unpaired electron, it is paramagnetic.

Dihydrides

While PbH2 remains uncharacterized, organic derivatives have been examined by X-ray crystallography including (C6H3-2,6-(mesityl)2)PbH dimer
CompoundChemical formulaMolecular geometrycomment
MethyleneCH2bent (134°)triplet ground state
SilyleneSiH2bent (92°)singlet ground state
GermyleneGeH2bentsinglet ground state
StanyleneSnH2bentsinglet ground state
PlumbylenePbH2unknownunknown

Trihydrides

CompoundChemical formulaMolecular geometrycomment
MethylCH3pyramidaldoublet ground state
Silyl radicalSiH3pyramidaldoublet ground state
SilanideSiH−3pyramidal
GermylGeH3pyramidaldoublet ground state
StanylSnH3pyramidaldoublet ground state
PlumbylPbH3unknownunknown

Tetrahydrides

The tetrahydrides have the chemical formula XH4, with X representing any of the carbon family. In the case of C, Si, Ge, and Sn, the tetrahydrides are tetrahedral monomers. PbH4 has not been verified experimentally, but it is predicted to be tetrahedral also on the basis of quantum chemical calculations.

CompoundChemical formulaMolecular geometrycomment
MethaneCH4tetrahedral, C-H distance is 108.7 pmmain component of natural gas
SilaneSiH4ttetrahedral, Si-H distance is 147 pmprecursor to silicon-based microelectronics
Germane
GeH4tetrahedral, Ge-H distance is 152.5 pmprecursor to germanium-based microelectronics
StannaneSnH4tetrahedral, Sn-H distance is 171 pmacademic interest
PlumbanePbH4uncertainstructure has not been verified experimentally

Anionic and cationic hydrides

Fragment of the BaSiH6 lattice. The [SiH6]2− center is apparent as the turquoise sphere (Si) surrounded by six white spheres (H). The H atoms link also to Ba2+ (red spheres).

Many anionic hydrides have been evaluated computationally but very few can be isolated. In organic chemistry, methyllithium is treated as the equivalent of the carbanion CH3-. Similarly, reagents such as trimethyloxonium tetrafluoroborate are treated as the equivalent of the carbocation CH3+.

Well-characterized hydride anions are salts of [SiH6]2-, an octahedral anion.

Catenated hydrides

Group 14 elements are renown for catenation, i.e. forming chains. The neutral hydrides are no exception. Hydrocarbons are a vast inventory of carbon hydrides. Oligomeric and polymeric silanes (see polysilane) and germanes (see polygermane) are far less extensive but have been shown to exist.


References

  1. ↑ Roy, Matthew M. D.; Omaña, Alvaro A.; Wilson, Andrew S. S.; Hill, Michael S.; Aldridge, Simon; Rivard, Eric (2021). "Molecular Main Group Metal Hydrides". Chemical Reviews. 121 (20): 12784–12965. doi:10.1021/acs.chemrev.1c00278. PMID 34450005.
  2. ↑ Encyclopedia of Astrobiology, Volume 1 edited by Ricardo Amils, José Cernicharo Quintanilla, Henderson James Cleaves, William M. Irvine, Daniele Pinti, Michel Viso. 2011, Springer: Heidelberg
  3. ↑ Queen, Joshua D.; Fettinger, James C.; Power, Philip P. (2019). "Two quasi-stable lead(II) hydrides at ambient temperature". Chemical Communications. 55 (69): 10285–10287. doi:10.1039/c9cc05106f. PMID 31396611.
  4. ↑ Shavitt, Isaiah (1985). "Geometry and singlet-triplet energy gap in methylene: A critical review of experimental and theoretical determinations". Tetrahedron. 41 (8): 1531–1542. doi:10.1016/S0040-4020(01)96393-8.
  5. ↑ Dubois, I. (1968). "The absorption spectrum of the free SiH2 radical". Canadian Journal of Physics. 46 (22): 2485–2490. doi:10.1139/p68-608.
  6. ↑ Wang, Xuefeng; Andrews, Lester (2003). "Infrared Spectra of Group 14 Hydrides in Solid Hydrogen: Experimental Observation of PbH4, Pb2H2, and Pb2H4". Journal of the American Chemical Society. 125 (21): 6581–6587. doi:10.1021/ja029862l. PMID 12785799.
  7. ↑ Ohno, Keiichi; Matsuura, Hiroatsu; Endo, Yasuki; Hirota, Eizi (1985). "The microwave spectra of deuterated silanes: SiH3D, SiH2D2, and SiHD3". Journal of Molecular Spectroscopy. 111: 73–82. doi:10.1016/0022-2852(85)90070-0.
  8. ↑ Beyer, Doreen C.; Spektor, Kristina; Vekilova, Olga Yu; Grins, Jekabs; Barros Brant Carvalho, Paulo H.; Leinbach, Logan J.; Sannemo-Targama, Michael; Bhat, Shrikant; Baran, Volodymyr; Etter, Martin; Sano-Furukawa, Asami; Hattori, Takanori; Kohlmann, Holger; Simak, Sergei I.; Häussermann, Ulrich (2025). "Synthesis of BaSiH6 Hydridosilicate at High Pressures─A Bridge to BaSiH8 Polyhydride". ACS Omega. 10 (15): 15029–15035. doi:10.1021/acsomega.4c10502. PMC 12019724. PMID 40290916.
  9. ↑ Puhakainen, Kati; Benson, Daryn; Nylén, Johanna; Konar, Sumit; Stoyanov, Emil; Leinenweber, Kurt; Häussermann, Ulrich (2012). "Hypervalent Octahedral SiH62−Species from High-Pressure Synthesis". Angewandte Chemie International Edition. 51 (13): 3156–3160. doi:10.1002/anie.201108713. PMID 22323241.
  10. ↑ Greenwood and Earnshaw, p. 301.

Bibliography