Complete ligand substitution and oxidation of the metal center in the photochemical reaction of CpM(CO)2I (M = Fe, Ru) with chelating β-diketones

Abstract

The visible-light irradiation of solutions of CpFe(CO)₂I (Cp = (η⁵-C₅H₅)), acetylacetone (or other β-diketones), and diisopropylamine in toluene led to the substitution of all ligands with β-diketonate anions and the oxidation of Fe^II to Fe^III. The only product was Fe(β-diketonate)₃, which exclusively formed even when using an equimolar ratio of CpFe(CO)₂I and diketone. The reaction occurred under both anaerobic and aerobic conditions. The proposed reaction mechanism assigns the key role to the non-innocent behavior of the β-diketonate ligands. Dioxygen or the acetylacetone acts as oxidant. The ruthenium complex CpRu(CO)₂I reacts with acetylacetone in a similar way to the corresponding iron complex, but irradiation with UV light is required to assure an acceptable yield of the product. All obtained complexes were analyzed by NMR, FT-IR, and ESI-MS, and one was subjected to single-crystal and powder X-ray diffraction analysis, which revealed its mer stereochemistry.