A novel method is described for the initiation and observation of metal ion-molecule reactions in dusters. A heterocluster composed of organometallic molecules and reactant species is formed by coexpansion in a supersonic jet. Photoionization of the precursor molecules by a picosecond, 266 nm laser pulse efficiently strips away the ligands, leaving metal ions and metal cluster ions in close proximity to reactant molecules. Subsequent ion-molecule reactions take place which are followed by monitoring the products by time-of-flight mass spectrometry. Using iron pentacarbonyl as an example, the formation of metal ions and cluster ions is demonstrated, and their reaction with nitric oxide and nitrous oxide is described.