Borane carbonyl

Borane carbonyl is the inorganic compound with the formula H₃BCO. This colorless gas is the adduct of borane and carbon monoxide. It is usually prepared by combining borane-ether complexes and CO. The compound is mainly of theoretical and pedagogical interest.^[2]

Borane carbonyl

Names
IUPAC name Borane carbonyl
Other names BH3CO Borane-carbon monoxide (1:1) Borane, compd. with carbon monoxide (1:1) Borine carbonyl Boron, carbonyltrihydro Boron, carbonyltrihydro-, (T-4)- Carbon monoxide-borane Carbonyltrihydroboron
Identifiers
CAS Number	13205-44-2
3D model (JSmol)	Interactive image
ChemSpider	10225684
PubChem CID	13212226
CompTox Dashboard (EPA)	DTXSID201337204
InChI InChI=1S/CO.BH3/c1-2;/h;1H3 Key: SJGVUIMZYFHURU-UHFFFAOYSA-N
SMILES [BH3-]C#[O+]
Properties
Chemical formula	H3BCO
Molar mass	41.84 g·mol−1
Appearance	colorless gas
Density	1.71 g/L[1]
Melting point	−137[1] °C (−215 °F; 136 K)
Boiling point	−64[1] °C (−83 °F; 209 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Structure and properties

The structure of the molecule of borane carbonyl is H₃B⁻−C≡O⁺. The B−C≡O linkage is linear. The coordination geometry around the boron atom is tetrahedral. The bond distances are 114.0 pm for the C≡O bond, 152.9 pm for the C−B bond, and 119.4 pm for the B−H bonds. The H−B−H bond angle is 113.7°. The C≡O vibrational band is at 2164.7 cm⁻¹, around 22 cm⁻¹ higher than that of free CO.^[3]

Borane carbonyl has an enthalpy of vaporization of 19.7 kJ/mol (4750 cal/mol).^[4] It has electronic state ¹A₁ and point group symmetry C_3v.^[5]

Synthesis and reactions

Borane carbonyl was discovered in 1937 by reacting diborane with excess carbon monoxide, with the equation:

B₂H₆ + 2 CO ⇌ 2 BH₃CO.^[4]

The reaction quickly reaches equilibrium at 100°C, but at room temperature, the reverse reaction is slow enough to isolate borane carbonyl. This reaction is performed at high pressures, typically with a maximum pressure observed of 1000 to 1600 psi (68.95 to 110.32 bar).^[6] It can also be performed at atmospheric pressure, with ethers as a catalyst.^[7][8]

A more recent synthesis of borane carbonyl involves slowly bubbling carbon monoxide through a 1 M H₃B−THF solution. The resulting gas stream can be condensed and subsequently bubbled through ethanolic potassium hydroxide to produce the boranocarbonate anion ([H₃BCO₂]²⁻ or H₃B⁻−CO−2).^[8]

References

1. "Borine carbonyl | 13205-44-2". www.chemicalbook.com.
2. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 165. ISBN 978-0-08-037941-8.
3. Jacobsen, H.; Berke, H.; Doering, S.; Kehr, G.; Erker, G.; Froehlich, R.; Meyer, O. (1999). "Lewis Acid Properties of Tris(pentafluorophenyl)borane. Structure and Bonding in L-B(C₆F₅)₃ Complexes". Organometallics. 18: 1724–1735. doi:10.1021/OM981033E.
4. Burg, Anton B.; Schlesinger, H. I. (1937-05-01). "Hydrides of Boron. VII. Evidence of the Transitory Existence of Borine (BH 3 ): Borine Carbonyl and Borine Trimethylammine". Journal of the American Chemical Society. 59 (5): 780–787. doi:10.1021/ja01284a002. ISSN 0002-7863.
5. NIST Chemistry WebBook. "NIST Chemistry WebBook". NIST Chemistry WebBook. Archived from the original on 2020-10-28. Retrieved 25 October 2020.
6. Carter, James C.; Parry, Robert W. (1965-06-01). "The Ammonia and Alkylamine Addition Compounds of Carbon Monoxide Borane". Journal of the American Chemical Society. 87 (11): 2354–2358. doi:10.1021/ja01089a009. ISSN 0002-7863.
7. Mayer, Erwin (1971-07-01). "Äther als Katalysatoren für die Reaktion von Diboran mit Lewis-Basen; vereinfachte Darstellung von Carbonylboran und Phosphinboran". Monatshefte für Chemie (in German). 102 (4): 940–945. doi:10.1007/BF00909917. ISSN 1434-4475.
8. Alberto, R.; Ortner, K.; Wheatley, N.; Schibli, R.; Schubiger, A. P. (2001). "Synthesis and Properties of Boranocarbonate: A Convenient in Situ CO Source for the Aqueous Preparation of [^99mTc(OH₂)₃(CO)₃]⁺". J. Am. Chem. Soc. 123 (13): 3135–3136. doi:10.1021/ja003932b. PMID 11457025.