Studies on olefin-co-ordinating transition-metal carbene complexes. Part 14. An unusual reaction of tricarbonyl(η4-cyclopenta-1,3-diene)iron: a new approach to acyldicarbonyl(η-cyclopentadienyl)iron complexes, and the X-ray crystal structure of [Fe(COC6H4CF3-p)(η-C5H5)(CO)2]

Abstract

Reaction of tricarbonyl(η⁴-cyclopenta-1,3-diene)iron (1) with aryl-lithium reagents, LiR (R = Ph, C₆H₄Me-o or -p, C₆H₄OMe-p, or C₆H₄CF₃-p), in diethyl ether at low temperature, followed by the reaction of the acylmetalate intermediates formed with Et₃OBF₄ in CH₂Cl₂ at –60 °C or in aqueous solution at 0 °C, afforded yellow crystalline compounds formulated as [Fe(COR)(η-C₅H₅)(CO)₂](2)–(6) based on elemental analyses, i.r., ¹H n.m.r., and mass spectra. Complex (6) has been studied by X-ray diffraction: triclinic, space group P with the unit-cell constants a= 7.670(7), b= 9.008(4), c= 10.662(1)Å, α= 103.70(2), β= 96.496(8), γ= 100.03(2)°, Z= 2, R= 0.039, and R′= 0.045 for 2 834 reflections with I > 3σ(I).