Carboranes are cage compounds composed of two carbons (the dots) and 10 borons (the other vertices of the cage). In the parent carborane there is a hydrogen (or another substituent) on every vertex.

This molecule in question is called 1,2-dehydro-o-carborane and is the carborane version of benzyne or 1,2-dehydrobenzene. Two hydrogens have been removed to make a strained high energy pi bond. Henry Gingrich came up with the following synthesis (following a route I thought had little chance).

Some reactions of this molecule are summarized in the following references:

Reactions of 1,2-Dehydro-o-carborane with Dienes, Ghosh, T.; Gingrich, H. L.; Kam, C. K.; Mobraaten, E. C.; Jones, M. Jr. J. Am. Chem. Soc. 1991,113, 1313.

Some Ene Reactions of 1,2-Dehydro-o-carborane, Huang, Q.; Gingrich, H. L.; Jones, M. Jr. Inorg. Chem. 1991, 30, 3254.

Reaction of 1,2-Dehydro-o-carborane with Acetylenes. Synthesis and Structure of a Carborane Analogue of Benzocyclobutadiene. Ho, D. M.; Cunningham, R. J.; Brewer, J. A.; Bian, N.; Jones, M., Jr. Inorg.Chem., 1995, 34, 5274.

Reaction of 1,2-Dehydro-o-carborane with Thiophenes. Cycloadditions and an Easy Synthesis of "Benzo-o-carboranes." Barnett-Thamattoor, L.; Zheng, G.-x.; Ho, D. M.; Jones, M. Jr.; Jackson, J. E. Inorg.Chem. 1996, 35, 7311.

Now, why bother? Why make such a strange and highly reactive molecule? In the parent carborane itself the carbon-carbon bond is very long, 1.63 Ångstroms. Why? Take a look at those two carbons - there are no less than six lines emanating from each one (the borons, too). They cannot be two-electron bonds. Carboranes are made up of a web of two-electron, three-center bonding.

It is extremely hard to stretch carbon-carbon bonds - molecules resist such distortion mightily. The carboranes present us with a quite rigid system in which the carbon-carbon bond is very long. We thought that we would have a chance to investigate a "stretched" pi bond if we could figure out how to get rid of the hydrogens on the carbons. Recently an undergraduate, Josh Atkins has come up with a new way to make 1,2-dehydro-o-carborane, the molecule you clicked. He takes advantage of Henry Gingrich's procedure to produce the adduct 1 from benzene. At about 230 C this molecule reverts to benzene and 1,2-dehydro-o-carborane, as shown by isolation of the naphthalene adduct. Thus he has provided us with a much cleaner source of 1,2-dehydro-o-carborane, and we should now be able to study many more reactions.

For Atkins' work see:

A New Source of 1,2-Dehydro-o-carborane. Atkins, J. H.; Ho, D. M.; Jones, M. Jr. Tetrahedron Lett. 1996, 37, 7217.