Cyclization of the pyruvyl(methoxycarbonyl)tetracarbonyliron complex cis-(CO)4Fe[C(O)C(O)CH3](CO2CH3) induced by pronucleophile reagents

International audience; Two iron complexes, cis-(CO)4Fe[C(O)C(O)CH3](CO2CH3) (1a) and cis-(CO)4Fe[C(O)CO2-CH2] [C(O)CH2] (3), are reported. Each complex can be considered as a λ-keto ester with a metal atom inserted into the chain linking its two organic groups. 1a is the only one found to evolve thermally, similarly to organic λ-keto esters, into the methoxy metallalactone (CO)4FeC(O)C(CH3)(OCH3)OC(O) (2a). This reaction is not reversible and does not require any acid or alkaline catalysis. The process does not result from a spontaneous dissociation of the methoxycarbonyl ligand of la but from an associative intra or intermolecular mechanism. A similar process can also be induced by pronuc…