The photochemistry of M₃(CO)₁₂ (M = Ru, Os) with pyrazole and its substituted derivatives

The photochemistry of M₃(CO)₁₂ [M = Ru (1a), Os (1b)] with pyrazole, 3,5-dimethylpyrazole, and 3,5-diphenylpyrazole is documented. With 1a, photolysis with pyrazole leads to the substitution product HRu₃(CO)₁₀(C₃H₃N₂) (2a). In the case of 1b, the initial product is the ortho-metallated species HOs₃(CO)₁₀(C₃H₃N₂) (3b), heating of which yields HOs₃(CO)₁₀(C₃H₃N₂) (2b). Photolysis of 1a and 1b with 3,5-dimethylpyrazole yields HRu₃(CO)₁₀(C₃HMe₂N₂) (4a) and HOs₃(CO)₁₀(C₃HMe₂N₂) (4b), respectively. The molecular structure of 4b has been determined by X-ray crystallography. There is no reaction on photolysis of 1a and 1b with 3,5-diphenylpyrazole.