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

This review probes C-(HX)-X-... 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-pi systems. In addition there are examples of C-(HH)-H-...-X dihydrogen bonding. Cage C-(HX)-X-... 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. (C) 2004 Elsevier B.V. All rights reserved.