Reactions of Fe₃(CO)₁₂ and Fe(CO)₅ with functionalized alkynes in CH₃OH-KOH solution - The crystal structure of Fe₂(CO)₆(PPh₃)[μ-η³- (H₂CCCH₂)]

The complex Fe₂(CO)₇(H₂CCCH₂) (1) is obtained starting from a variety of functionalized alkynes that can release C₃ fragments during the reactions with Fe₃(CO) ₁₂ or Fe(CO)₅ in CH₃OH-KOH solutions. Owing to the oily nature of 1, it was reacted with triphenylphosphine, and the structure of the resulting title compound (1a) has been determined by X-ray analysis. Complex 1a shows a new coordination mode of a H₂C=C=CH₂ ligand to a diiron centre and is, to our knowledge, unprecedented. We have also found that 1 (and 1a) are by-products, and not intermediates in the formation of complex 3. A discussion of the possible reaction pathways is given.