Ground state Al atoms activate the C-Br bond of bromocyclopropane to give (CpAlBr)-Br-79, (CpAlBr)-Br-81 and allyl. DFT calculations of the nuclear hyperfine interaction are comparable to the values extracted from the EPR spectra. An examination of the potential energy hypersurface at the B3LYP level for an Al atom approaching bromocyclopropane suggests that the favored reaction in the gas phase should be the formation of AlBr and cyclopropyl. Therefore, it is argued that following AlBr abstraction cyclopropyl participates in two competing reactions: (i) it can undergo ring opening to yield allyl [H2CCHCH2](center dot) or (ii) cyclopropyl can combine with AlBr to form CpAlBr. (c) 2005 Elsevier B.V. All rights reserved.