Studies on olefin-co-ordinating transition metal carbene complexes. Part 12. Novel synthesis and structural characterization of (η6-arene)dicarbonyliron complexes, and their oxidation products

Abstract

The complexes [Fe(CO)₂{η⁶-RC₆H₄C(OX)(C₈H₁₂)}][X = SiMe₃, R = H (2), m-Me(3), p-Me (4), or p-Ph (5); X = Et, R = H (6) or p-Me (7)] have been prepared by the novel reaction of tricarbonyl(cyclo-octa-1,5-diene)iron (1) with aryl-lithium reagents in diethyl ether at low temperature, followed by alkylation of the adducts formed with SiMe₃Cl or Et₃OBF₄. The oxidation of (2) and (4) with [NH₄]₂[Ce(NO₃)₆] in ethanol solution at low temperature led to dissociation of the Fe(CO)₂ moiety to give 9-aryl-9-trimethylsiloxybicyclo[4.2.1]non-2-ene (aryl = Ph or p-MeC₆H₄) in high yields. The new compounds were characterized by elemental analyses, i.r., ¹H n.m.r., and mass spectra. In addition, the structure of complex (4) was confirmed unambiguously by X-ray diffraction analyses: triclinic, space group P, with a= 9.689(3), b= 9.801(2), c= 13.185(7)Å, α= 75.20(3), β= 68.19(3), γ= 64.47(2)°, Z= 2; R= 0.036 and R′= 0.026 for 3 166 reflections with I 3σ(I).