Cage C-H ... dot X interactions in solid-state structures of icosahedral carboranes.

This review probes C---HX interactions involving the acidic cage-carbon C---H bonds in ortho-, meta- and para-carboranes, closo-C2B10H12, and their derivatives, by examining the structurally characterised examples from the Cambridge Structural Database and other sources. Examples are examined of weak hydrogen bonds to X=O, N, S, F, Cl, Br, I, plus alkyne, cyclopentadienyl and arene-π systems. In addition there are examples of C---HH-X dihydrogen bonding. Cage C---HX interactions can be used to account for the observation of ordered structures in examples of carboranes where disorder of C and B cage atoms is possible