The reactions of 3-alkyl-1-ethylalumacyclopentanes with allyl halides in the presence of Ni(acac)(2) as a catalyst were studied by dynamic NMR spectroscopy. Under the action of Ni complexes, alumacyclopentanes initially undergo intramolecular hydride transfer to give but-3-enyl(ethyl)aluminum hydrides and then react with the starting allyl halide, yielding but-3-enyl(ethyl)aluminum halides. Subsequent intramolecular carboalumination affords the corresponding 1,1-disubstituted cyclopropanes.