Carboryne

In organoboron chemistry, a carboryne is an unstable derivative of ortho-carborane with the formula B10C2H10. They are also called 1,2-dehydro-o-carboranes. The hydrogen atoms on the C2 unit in the parent o-carborane are missing. The compound resembles and is isolobal with benzyne. A carboryne compound was first generated in 1990 starting from o-carborane. The hydrogen atoms connected to carbon are removed by n-butyllithium in tetrahydrofuran and the resulting lithium dianion is reacted with bromine at 0 °C to form the bromo monoanion.


 * [[Image:Carboryne synthesis.png|600px|Carboryne synthesis, main chemical bonds involving carbon in red]]

Heating the reaction mixture to 35 °C releases carboryne, which can subsequently be trapped with suitable dienes:
 * [[Image:Carboryne reactions.png|600px|carboryne reactions]]

such as anthracene (to afford a triptycene-like molecule) and furan in 10 to 25% chemical yield.

Carborynes react with alkynes to benzocarboranes in an adaptation of the above described procedure. O-carborane is deprotonated with n-butyllithium as before and then reacted with dichloro-di(triphenylphosphino) nickel to a nickel coordinated carboryne. This compound reacts with 3-hexyne in an alkyne trimerization to the benzocarborane.


 * [[Image:BenzocarboraneSynthesis.png|600px|benzocarborane synthesis]]

Single crystal X-ray diffraction analysis of this compound shows considerable bond length alternation in the benzene ring (164.8 pm to 133.8 pm) ruling out aromaticity.