Metal carbonyl chemistry. Part XIX. Diels–Alder reactions of the π-cyclopentadienyldicarbonyliron derivative of hexafluorobicyclo[2.2.0]hexa-2,5-diene

Abstract

The compound [(p-C₆F₅)Fe(CO)₂(π-C₅H₅)] reacts with cyclopentadiene, furan, or 2.3-dimethylbuta-1,3-diene to give yellow, air-stable 1 : 1 Diels–Alder adducts in which the para-bond is retained. Pyrrole failed to react under similar conditions. The i.r. spectra of the adducts from cyclopentadiene and furan show evidence for the presence of rotational isomers about the iron atom. The adduct from cyclopentadiene has also been prepared in low yield from reaction of 2,3,4,5,6,7-hexafluorotetracyclo[6.2.1.0^2,7.0^3,6]undeca-4,9-diene (the Diels–Alder adduct of cyclopentadiene and para-hexafluorobenzene) with Na[Fe(CO₂)(π-C₅H₅)], but attempts to prepare the furan and pyrrole adducts by a similar route were unsuccessful.