The infrared spectra of the species derived from dicarbonyl(η 5 -cyclopentadienyl)iron(0) {[CpFe(CO) 2 ] 2 (Cp = η 5 -C 5 H 5 )} which are supported on the surfaces of acidic, neutral, and basic alumina (Al 2 O 3 ) have been measured. The structures and stabilities of these supported organometallic species depend markedly on the acid-base properties of the alumina surfaces.