Borane carbonyl is the inorganic compound with the formula . 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.
Structure and properties
The structure of the molecule of borane carbonyl is . The linkage is linear. The coordination geometry around the
boron atom is tetrahedral. The bond distances are 114.0
picometre for the bond, 152.9 pm for the bond, and 119.4 pm for the bonds. The bond angle is 113.7°. The vibrational band is at 2164.7 cm
−1, around 22 cm
−1 higher than that of free
carbon monoxide.
Borane carbonyl has an enthalpy of vaporization of 19.7 Kilojoule/mol (4750 Calorie/mol).
Synthesis and reactions
Borane carbonyl was discovered in 1937 by reacting
diborane with excess carbon monoxide, with the equation:
- .
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).
It can also be performed at atmospheric pressure, with
as a
catalyst.
A more recent synthesis of borane carbonyl involves slowly bubbling carbon monoxide through a 1 M solution. The resulting gas stream can be condensed and subsequently bubbled through Ethanol potassium hydroxide to produce the boranocarbonate anion ( or ).
