Metal–carbonyl and metal–nitrosyl complexes. Part XIV. Molecular structure of the allyltricarbonyliron cation intermediate in the friedel–crafts acetylation of butadienetricarbonyliron: X-ray study of tricarbonyl(1–3-η-hexen-5-one)iron hexafluorophosphate

Abstract

The molecular geometry of the title cation has been determined by X-ray analysis of its hexafluorophosphate salt. The tricarbonyliron group is bound to the allyl fragment and the oxygen atom of the CH₂CHCH·CH₂·CO·CH₃ ligand, with Fe–C 2·141 (10), 2·063(9), and 2·144(8) and Fe–O 1·999(5)Å. The Fe–CO bond trans to oxygen is 1·787(7)Å, whilst those trans to allyl are 1·840(9) and 1·828(8)Å. The mean P–F separation in the hexafluorophosphate anion is 1·578(9)Å. The complex crystallizes in the orthorhombic space group Pbca, with Z= 8 and a= 15·136(11), b= 15·256(8), c= 12·123(10)Å. X-Ray intensity data were collected on a diffractometer, and the atomic parameters were determined by Fourier and least-squares methods, the final R being 7·1% over 2365 independent reflections.