The Bent Bonds of Cubane
The carbon–carbon bonding in cubane is shown not to be along the C–C vectors between carbon atoms at the corners of a cube. Instead, the bonding is “bent” as seen in a new single-crystal X-ray structure of cubane at 93 K. The bent bond angles and lengths are compared with the geometric angles and with predictions. The distortions from the tetrahedral angle of the sp3-hybridized carbon atoms are shown to be relatively small in cubane, unlike those in cyclopropane, which are large. Despite this and other differences, cubane and cyclopropane have similar reactivity, a fact that has not been widely recognized. It is suggested that cubane might mimic the chemistry of the cyclopropane ring in the pharmacology of some cyclopropane-containing drugs.