Boron monohydride

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Boron monohydride
Boron monohydride.png
IUPAC name
3D model (JSmol)
PubChem CID
  • InChI=1S/BH/h1H
  • DB:InChI=1S/BH/h1H/i1D
  • TB:InChI=1S/BH/h1H/i1T
  • BH:[BH]
  • DB:[2H][B]
  • TB:[3H][B]
Molar mass 11.82 g·mol−1
Thermochemistry [1]
Std molar
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Borane(1), boron monohydride, hydridoboron or borylene is the molecule with the formula BH. It exists as a gas but rapidly degrades when condensed. By contrast, the cluster B12H122- (dodecaborate), which has very similar empirical formula, forms robust salts.



Boron monohydride can be formed from borane carbonyl exposed to ultraviolet light. BH3CO → BH + CH2O [2]

Boron monohydride is formed when boron compounds are heated to a high temperature in the presence of hydrogen. [3]

Boron monohydride is formed when the boron anion B reacts with a hydrogen ion H+. It is also formed when atomic boron reacts with hydrogen. B + H2 → BH + H. There is too much energy in the reaction for BH2 to be stable. [4]

Boron monohydride probably exists in sunspots, [5] but as of 2008 has not been detected. [6]


The ionization potential is around 9.77  eV. [7] The dissociation energy for the ground state molecule is 81.5 kcal/mol. [8] The electron affinity is roughly 0.3 eV, and the HB ion is formed. [9]

The dipole moment of the molecule in its ground state is 1.27 debye and for the first excited electronic state A1Π is 0.58 debye. [10]

The spectrum of boron monohydride includes a molecular band for the lowest electronic transition X1Σ+ → A1Π with a band head at 433.1 nm (for 0→0) and 437.1 (for 0→1) [3] The spectrum contains P, Q, and R branches. [10]

Although BH is a closed shell molecule, it is paramagnetic independent of temperature. [11]


Boron monohydride is unstable in bulk and disappears quickly on a timescale of 20 ns when at a pressure of 20 Torr. [12] Boron monohydride reacts with oxygen, probably forming HBO. [2] Boron monohydride shows no reaction with methane, but reacts with propane to give C3H7BH2. With nitric oxide (NO) it probably yields HBO and HBNO. Boron monohydride appears to add onto double bonds in unsaturated organic compounds. It also reacts with water. [2]

Boron monohydride can take on the form of solid poly-borane(1) which spontaneously inflames in air. [13]

Solid BH is predicted to take on an Ibam phase at pressures over 50 GPa and then become a metallic P6/mmm phase over 168 GPa. [14]


Both a cation and a dication are known. The dication HB2+ can be supported by a σ-donating ligand framework with two links. [15] The dianion can also be stabilized by an amine. [16]

Related Research Articles

In chemistry, hydronium (hydroxonium in traditional British English) is the common name for the aqueous cation H3O+, the type of oxonium ion produced by protonation of water. It is often viewed as the positive ion present when an Arrhenius acid is dissolved in water, as Arrhenius acid molecules in solution give up a proton (a positive hydrogen ion, H+) to the surrounding water molecules (H2O). In fact, acids must be surrounded by more than a single water molecule in order to ionize, yielding aqueous H+ and conjugate base. Three main structures for the aqueous proton have garnered experimental support: the Eigen cation, which is a tetrahydrate, H3O+(H2O)3, the Zundel cation, which is a symmetric dihydrate, H+(H2O)2, and the Stoyanov cation, an expanded Zundel cation, which is a hexahydrate: H+(H2O)2(H2O)4. Spectroscopic evidence from well-defined IR spectra overwhelmingly supports the Stoyanov cation as the predominant form. For this reason, it has been suggested that wherever possible, the symbol H+(aq) should be used instead of the hydronium ion.

<span class="mw-page-title-main">Boranes</span>

A borane is a compound with the formula BxHy or a related anion. Many such boranes are known. Most common are those with 1 to 12 boron atoms. Although they have few practical applications, the boranes exhibit structures and bonding that differs strongly from the patterns seen in hydrocarbons. Hybrids of boranes and hydrocarbons, the carboranes are also well developed.

<span class="mw-page-title-main">Diborane</span> Chemical compound

Diborane(6), commonly known as diborane, is the chemical compound with the formula B2H6. It is a toxic, colorless, and pyrophoric gas with a repulsively sweet odor. Given its simple formula, borane is a fundamental boron compound. It has attracted wide attention for its electronic structure. Several of its derivatives are useful reagents.

In chemistry, dimerization refers to the process of joining two molecules or ions by bonds. The resulting bonds can be either strong or weak. Many symmetrical chemical species are described as dimers, even when the monomer is unknown or highly unstable.

<span class="mw-page-title-main">Ammonia borane</span> Chemical compound

Ammonia borane (also systematically named Ammoniotrihydroborate), also called borazane, is the chemical compound with the formula H3NBH3. The colourless or white solid is the simplest molecular boron-nitrogen-hydride compound. It has attracted attention as a source of hydrogen fuel, but is otherwise primarily of academic interest.

<span class="mw-page-title-main">Adduct</span> Product of direct addition of two or more distinct molecules

In chemistry, an adduct is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all components. The resultant is considered a distinct molecular species. Examples include the addition of sodium bisulfite to an aldehyde to give a sulfonate. It can be considered as a single product resulting from the direct combination of different molecules which comprises all atoms of the reactant molecules.

<span class="mw-page-title-main">Methanium</span> Ion of carbon with five hydrogens

In chemistry, methanium is a complex positive ion with formula [CH5]+ or [CH3(H2)]+, bearing a +1 electric charge. It is a superacid and one of the onium ions, indeed the simplest carbonium ion.

A frustrated Lewis pair (FLP) is a compound or mixture containing a Lewis acid and a Lewis base that, because of steric hindrance, cannot combine to form a classical adduct. Many kinds of FLPs have been devised, and many simple substrates exhibit activation.

<span class="mw-page-title-main">Thiophosphoryl fluoride</span> Chemical compound

Thiophosphoryl fluoride is an inorganic molecular gas with formula PSF3 containing phosphorus, sulfur and fluorine. It spontaneously ignites in air and burns with a cool flame. The discoverers were able to have flames around their hands without discomfort, and called it "probably one of the coldest flames known". The gas was discovered in 1888.

<span class="mw-page-title-main">Chromium(I) hydride</span> Chemical compound

Chromium(I) hydride, systematically named chromium hydride, is an inorganic compound with the chemical formula (CrH)
. It occurs naturally in some kinds of stars where it has been detected by its spectrum. However, molecular chromium(I) hydride with the formula CrH has been isolated in solid gas matrices. The molecular hydride is very reactive. As such the compound is not well characterised, although many of its properties have been calculated via computational chemistry.

Borane, also known as borine, is an unstable and highly reactive molecule with the chemical formula BH
. The preparation of borane carbonyl, BH3(CO), played an important role in exploring the chemistry of boranes, as it indicated the likely existence of the borane molecule. However, the molecular species BH3 is a very strong Lewis acid. Consequently, it is highly reactive and can only be observed directly as a continuously produced, transitory, product in a flow system or from the reaction of laser ablated atomic boron with hydrogen. It normally dimerizes to diborane in the absence of other chemicals.

<span class="mw-page-title-main">Calcium monohydride</span> Chemical compound

Calcium monohydride is a molecule composed of calcium and hydrogen with formula CaH. It can be found in stars as a gas formed when calcium atoms are present with hydrogen atoms.

<span class="mw-page-title-main">Magnesium monohydride</span> Chemical compound

Magnesium monohydride is a molecular gas with formula MgH that exists at high temperatures, such as the atmospheres of the Sun and stars. It was originally known as magnesium hydride, although that name is now more commonly used when referring to the similar chemical magnesium dihydride.

<span class="mw-page-title-main">Dodecaborate</span> Chemical compound

The dodecaborate(12) anion, [B12H12]2−, is a borane with an icosahedral arrangement of 12 boron atoms, with each boron atom being attached to a hydrogen atom. Its symmetry is classified by the molecular point group Ih.

<span class="mw-page-title-main">1,2-Dimethyldiborane</span> Chemical compound

1,2-Dimethyldiborane is an organoboron compound with the formula [(CH3)BH2]2. Structurally, it is related to diborane, but with methyl groups replacing terminal hydrides on each boron. It is the dimer of methylborane, CH3BH2, the simplest alkylborane. 1,2-Dimethyldiborane can exist in a cis- and a trans arrangement. 1,2-Dimethyldiborane is an easily condensed, colorless gas that ignites spontaneously in air.

<span class="mw-page-title-main">Tetramethyldiborane</span> Chemical compound

Dimethylborane, (CH3)2BH is the simplest dialkylborane, consisting of a methyl group substituted for a hydrogen in borane. As for other boranes it normally exists in the form of a dimer called tetramethyldiborane or tetramethylbisborane or TMDB ((CH3)2BH)2. Other combinations of methylation occur on diborane, including monomethyldiborane, trimethyldiborane, 1,2-dimethylborane, 1,1-dimethylborane and trimethylborane. At room temperature the substance is at equilibrium between these forms. The methylboranes were first prepared by H. I. Schlesinger and A. O. Walker in the 1930s.

<span class="mw-page-title-main">Trimethyldiborane</span> Chemical compound

Trimethyldiborane, (CH3)3B2H3 is a molecule containing boron carbon and hydrogen. It is an alkylborane, consisting of three methyl group substituted for a hydrogen in diborane. It can be considered a mixed dimer: (CH3)2BH2BH(CH3) or dimethylborane and methylborane. called 1,2-dimethyldiborane. Other combinations of methylation occur on diborane, including monomethyldiborane, 1,2-dimethyldiborane, tetramethyldiborane, 1,1-dimethylborane and trimethylborane. At room temperature the substance is at equilibrium between these forms, so it is difficult to keep it pure. The methylboranes were first prepared by H. I. Schlesinger and A. O. Walker in the 1930s.

<span class="mw-page-title-main">Methyldiborane</span> Chemical compound

Methyldiborane, CH3B2H5, or monomethyldiborane is the simplest of alkyldiboranes, consisting of a methyl group substituted for a hydrogen in diborane. As with other boranes it exists in the form of a dimer with a twin hydrogen bridge that uses three-center two-electron bonding between the two boron atoms, and can be imagined as methyl borane (CH3BH2) bound to borane (BH3). Other combinations of methylation occur on diborane, including 1,1-dimethylborane, 1,2-dimethyldiborane, trimethyldiborane, tetramethyldiborane, and trimethylborane (which is not a dimer). At room temperature the substance is at equilibrium between these molecules.

Diborane(2), also known as diborene, is an inorganic compound with the formula B2H2. The number 2 in diborane(2) indicates the number of hydrogen atoms bonded to the boron complex. There are other forms of diborane with different numbers of hydrogen atoms, including diborane(4) and diborane(6).

<span class="mw-page-title-main">1,1-Dimethyldiborane</span> Chemical compound

1,1-Dimethyldiborane is the organoboron compound with the formula (CH3)2B(μ-H)2BH2. A pair of related 1,2-dimethyldiboranes are also known. It is a colorless gas that ignites in air.


  1. "GROMACS Molecule Database - boron-monohydride". Archived from the original on 2021-07-10. Retrieved 2019-07-22.
  2. 1 2 3 Garland, Nancy L.; Stanton, C. T.; Fleming, James W.; Baronavski, A. P.; Nelson, H. H. (June 1990). "Boron monohydride reaction kinetics studied with a high-temperature reactor". The Journal of Physical Chemistry. 94 (12): 4952–4956. doi:10.1021/j100375a036.
  3. 1 2 Abad, Carlos; Florek, Stefan; Becker-Ross, Helmut; Huang, Mao-Dong; Heinrich, Hans-Joachim; Recknagel, Sebastian; Vogl, Jochen; Jakubowski, Norbert; Panne, Ulrich (October 2017). "Determination of boron isotope ratios by high-resolution continuum source molecular absorption spectrometry using graphite furnace vaporizers". Spectrochimica Acta Part B: Atomic Spectroscopy. 136: 116–122. Bibcode:2017AcSpe.136..116A. doi:10.1016/j.sab.2017.08.012.
  4. Yang, Xuefeng; Dagdigian, Paul J. (1993). "Chemiluminescence spectra and cross sections for the reaction of boron(4p 2P) with hydrogen and deuterium". The Journal of Physical Chemistry. 97 (17): 4270–4276. doi:10.1021/j100119a006. ISSN   0022-3654.
  5. Engvold, O. (February 1970). "The diatomic molecules BH, BN, and BO in sunspots and the solar abundance of boron". Solar Physics. 11 (2): 183–197. Bibcode:1970SoPh...11..183E. doi:10.1007/BF00155219. S2CID   119720128.
  6. Karthikeyan, B; Bagare, S; Rajamanickam, N; Raja, V (February 2009). "On the search for BF, BH and BS molecular lines in sunspot spectra". Astroparticle Physics. 31 (1): 6–12. Bibcode:2009APh....31....6K. doi:10.1016/j.astropartphys.2008.10.009.
  7. Haynes, William M. (2012). CRC Handbook of Chemistry and Physics, 93rd Edition. CRC Press. pp. 10–200. ISBN   9781439880494.
  8. Bauschlicher, Charles W.; Langhoff, Stephen R.; Taylor, Peter R. (July 1990). "On the dissociation energy of BH". The Journal of Chemical Physics. 93 (1): 502–506. Bibcode:1990JChPh..93..502B. doi:10.1063/1.459550.
  9. Reid, C.J. (August 1993). "Electron affinities of BH, B2, BC and BN molecules determined using charge inversion spectrometry". International Journal of Mass Spectrometry and Ion Processes. 127: 147–160. Bibcode:1993IJMSI.127..147R. doi:10.1016/0168-1176(93)87087-9.
  10. 1 2 Thomson, Ritchie; Dalby, F. W. (June 1969). "An experimental determination of the dipole moments of the X ( 1 Σ) and A ( 1 Π) states of the BH molecule". Canadian Journal of Physics. 47 (11): 1155–1158. Bibcode:1969CaJPh..47.1155T. doi:10.1139/p69-144.
  11. Fowler, P.W.; Steiner, E. (20 December 1991). "Paramagnetic closed-shell molecules: the isoelectronic series CH + , BH and BeH -". Molecular Physics. 74 (6): 1147–1158. Bibcode:1991MolPh..74.1147F. doi:10.1080/00268979100102871.
  12. Bauer, S. H. (January 1996). "Oxidation of B, BH, BH3, and BmHn Species: Thermochemistry and Kinetics". Chemical Reviews. 96 (6): 1907–1916. doi:10.1021/cr941034q. PMID   11848815.
  13. Urben, Peter (2013). Bretherick's Handbook of Reactive Chemical Hazards. Elsevier. p. 71. ISBN   9780080523408.
  14. Hu, Chao-Hao; Oganov, Artem R.; Zhu, Qiang; Qian, Guang-Rui; Frapper, Gilles; Lyakhov, Andriy O.; Zhou, Huai-Ying (19 April 2013). "Pressure-Induced Stabilization and Insulator-Superconductor Transition of BH". Physical Review Letters. 110 (16): 165504. Bibcode:2013PhRvL.110p5504H. doi: 10.1103/PhysRevLett.110.165504 . PMID   23679618.
  15. Chen, Wen-Ching; Lee, Ching-Yu; Lin, Bo-Chao; Hsu, Yu-Chen; Shen, Jiun-Shian; Hsu, Chao-Ping; Yap, Glenn P. A.; Ong, Tiow-Gan (10 January 2014). "The Elusive Three-Coordinate Dicationic Hydrido Boron Complex". Journal of the American Chemical Society. 136 (3): 914–917. doi:10.1021/ja4120852. PMID   24383448.
  16. Vargas-Baca, Ignacio; Findlater, Michael; Powell, Adam; Vasudevan, Kalyan V.; Cowley, Alan H. (2008). "Boron di- and tri-cations". Dalton Transactions (45): 6421–6. doi:10.1039/b810575h. PMID   19002329. S2CID   20702130.