Visible-light irradiation of FeCp (p-xyl)+(Cp= cyclopentadienyl, p-xyl= p-xylene) in organic solvents in the presence of suitableligands leads to the formationof products in which the three coordination sites occupied by p-xylene have been replaced to give complexes of the form FeCpL3+(L3=(p-CNPhCH3) 3,(CO) 3, hexamethylbenzene, and triphos), which have been isolated and characterized as PF6~ or BF4" salts. The quantum yields for the formation of these products are rather large. For example, irradiation (436 nm) of the LF bands of FeCp (p-xyl)+ in methylene chloride in the presence of 0.05 M triphos (bis (2-(diphenylphosphino) ethyl) phenylphosphine) yields FeCp (triphos)" 1" with= 0.57±0.06. The course of the photochemical reaction was different in methylene chloride solution with 1, 10-phenanthrolineadded or in aqueous 0.1 Nh2s04 solution. The 436-nm irradiationof FeCp (p-xyl)+ in methylene chloride in the presence of 0.1 M 1, 10-phenanthroline leads to the formation of Fe (phen) 32+ with a quantum yield of 0.58±0.06. Similarly, 436-nm-irradiation of FeCp (p-xyl)+ in 0.1 N aqueous H2S04 solution leads to the formation of Fe2+(aq) with a quantum yield of 0.81±0.08. The possible mechanisms for these reactions are tentatively discussed in terms of replacement of p-xylene to produce a reactive transition-metal fragment containing the FeCp+ unit, which undergoes addition of incoming ligand L to form complexes of the form FeCpL3+ or FeL „2+.