Thermal properties and reactions towards nucleophiles of an iron complex displaying an acetyl and a pyruvoyl ligands

Abstract

Thermal evolution at 4 °C of the structurally characterized cis(CO) 4Fe[C(O)C(O)CH 3][C(O)CH 3] ( 1( 2)) gives rise to the cis(CO) 4Fe[C(O)CH 3] 2 ( 1( 3)) which, probably owing to synthetic problems, has never been described in the literature. By reaction with anionic nucleophiles (Nu −), 1( 2) affords anionic trifunctionalized metallalactones {(CO) 3Fe[C(O)CH 3][C(O)C(CH 3)(Nu)OC 7(O);(Fe–C 7)]} − ( 3) formed by addition of the nucleophile reagent on the β carbon of the pyruvoyl moiety followed by the cyclization of this ligand on a terminal carbonyl of the complex. Anions 3 are characterized by 1H and 13C NMR and by X-ray diffraction for the complex with Nu = C(H)(CO 2C 2H 5) 2. Complexes 3 are also prepared by reaction of CH 3Li with the neutral metallalactones (CO) 4Fe[C(O)C(CH 3)(Nu)OC 7(O);Fe– 7C] ( 2). The results of this study shed light on the reaction of cyclization of a pyruvoyl ligand as they clearly show that the presence of a second ligand (for example CO 2R) with a labile OR group is not required to perform the formation of the metallalactone ring and then that the observed reaction has no connection with organic chain-ring transformations.