Structural evidence for antiaromaticity in free boroles

Abstract

(Chemical Equation Presented) Pentaphenylborole and a ferrocenylborole were synthesized and structurally characterized. Both experimental and theoretical data reveal that rather weak intermolecular interactions are able to significantly alter the bond lengths in the borole ring of pentaphenylborole (see picture). Moreover, the high Lewis acidity of boroles is demonstrated by a significant Fe⋯B interaction in the ferrocenylborole in the solid state. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.