Photoinduced Fragmentation of H₃Re₃(CO)₁₂ and H₃Mn₃(CO)₁₂

Ultraviolet irradiation of H₃Re₃(CO)i₂in degassed solution leads to quantitative formation of H₂Re₂(CO)₈. Quantum yields measured at 313 and 366 nm are of the order of 0.1. Photolysis in the presence of CO also gives fragmentation and formation of HRe(CO)₅and H₂Re₂(CO)5, but the latter thermally reacts with CO to form HRe(CO)5 and Re₂(CO)10. The quantum yield of disappearance of H₃Re₃(CO)₁₂in the presence of CO is 0.02. Photolysis of the analogous H₃Mn₃(CO)₁₂cluster produces HMn(CO)₅, Mn₂(CO)₁₀, and an unidentified brown precipitate. Experiments directed toward elucidating the mechanism of these photoreactions are discussed.