Ligand lability in carbonyl(η-cyclopentadienyl)triphenylphosphineiron derivatives

Abstract

(σ-Allyl)carbonyl(µ-cyclopentadienyl)triphenylphosphineiron undergoes a clean first-order associative process above 40 °C with formation of (1–3-η-allyl)carbonyl(η-cyclopentadienyl) iron and triphenylphosphine, at a rate virtually independent of solvent. Protonation of the former gives a cationic η-propene complex which is very reactive in solution with respect to loss of propene, but more stable in the solid state. Two diastereoisomeric complexes have been observed by n.m.r. spectroscopy in SO₂ at –10 °C which gradually release propene to form a further cationic species. Carbonyl(η-cyclopentadienyl)halogeno(triphenylphosphine)iron complexes react under a range of conditions in the presence of Lewis acids to form dicarbonyl(η-cyclopentadienyl)iron derivatives.