Synthesis of a new iron tricarbonyl (η4)-α-pyrone complex by reaction of iron vinyldiketone complexes with methyllithium under a CO atmosphere

A synthetic, structural and reactivity study of [(η4-C4R4)Co(η5-C5H4X)] complexes, R=Me or Et; X=CHO, CHCHFc, CHCH(η5-C5H4)Co(η4-C4Ph4), CHC(CN)2: Unexpected formation of [(η5-cyclopentadienyl)(η4-3,4,5,6-tetraethyl-α-pyrone)cobalt]

“…The C 4 Et 4 unit deviates from parallelism with the C 5 H 5 ring by 7°, and the angle C 4 Et 4 (centroid)-Co-C 5 H 5 (centroid) is 172.7°. The interplanar angle between the tetraethylbutadiene moiety and the CO 2 fragment is 42.7°, similar to the fold angles previously observed (40-42°) in other (a-pyrone)Fe(CO) 3 and (a-pyrone)-Co(C 5 H 5 ) complexes [43,[52][53][54]. As seen in molecules 4 and 11(Z), three of the ethyl substituents are oriented axially distal while the fourth is rotated almost into the plane of the butadiene.…”

Iron(0) Promotes Aza Cyclization of an Elusive Ferrocenylketene

“…The structure of 3 was fully established through an X-ray diffraction analysis (Figure ). According to the data gathered, no significant differences in the geometry and bond distances around the ketene moiety can be seen on going from other (η 4 -vinylketene)iron(0) complexes containing simple substituents such as alkyl or aryl groups . It is important to point out that the structure of this compound includes a ferrocenyl moiety, which is a strongly electron donating group, that can be an important factor in the instability of the ketene; the presence of [Fe(CO) 3 ] as a protector group thus helps to trap this reactive intermediate.…”

“…The synthesis and study of ferrocenylvinylketenes have been restricted to just a few examples, which could be due to their high predicted instability. , Tidwell and co-workers developed the synthesis of ferrocenylketenes through a Wolff rearrangement, providing evidence for the presence of this intermediate using time-resolved IR spectroscopy and trapping it by reaction with n -BuNH 2 to give the corresponding amide. An efficient alternative for synthesizing these kind of masked intermediates as stable and isolable compounds could be the use of iron(0) complexes, − starting from available α,β-unsaturated ferrocenyl ketones. Such ligands can be versatile precursors that can incorporate a wide variety of groups, including aza-heterocyclic rings.…”