In organic chemistry, a carbyne is a general term for any compound whose structure consists of an electrically neutral carbon atom connected by a single covalent bond and has three non-bonded electrons. The carbon atom has either one or three unpaired electrons, depending on its excitation state; making it a radical. The chemical formula can be written or (also written as ), or just CH.
Carbynes can be seen as derivatives of the simplest such compound, the methylidyne radical or unsubstituted carbyne or , in which the functional group is a hydrogen atom.
Electronic configuration
Carbyne molecules are generally found to be in electronic doublet states: the non-bonding electrons on carbon are arranged as one radical (unpaired electron) and one electron pair, leaving a vacant atomic orbital, rather than being a triradical (the quartet state). The simplest case is the CH radical, which has an electron configuration .
Carbynes can act as trivalent ligands in complexes with transition metals, in which they are connected to a metal by the three non-bonded electrons in the –C<sup>3•</sup> group. Examples of such coordination compounds are , WBr(CO)<sub>2</sub>(2,2'-bipyridine)≡C-aryl and WBr(CO)<sub>2</sub>(PPh<sub>3</sub>)<sub>2</sub>≡C-NR<sub>2</sub>. Such a compound can be obtained by the reaction of tungsten hexacarbonyl W(CO)<sub>6</sub> with lithium diisopropylamide to form (<sup>i</sup>Pr<sub>2</sub>N)(OLi)C=W(CO)<sub>5</sub>. This salt is then oxidized with either oxalyl bromide or triphenylphosphine dibromide, followed by addition of triphenylphosphine. Another method is to treat a methoxy metal carbene with a Lewis acid.