Formation and X-ray structure of the μ-alkylidene complex Fe2(CO)6(μ-η3, η3-C(CH=CHPh)2) upon deoxygenation of Fe2(CO)8(μ-η2, η2-C(O) (CH=CHPh)2) with methyl lithium

Article abstract of DOI:10.1016/0022-328X(95)05457-Z

Di-iron nonacarbonyl reacts with dibenzylideneacetone (5) to produce, depending on the reaction conditions, either a mixture of the three complexes Fe(CO4<η²(CO)(CH=CHPh)2> (6), Fe2(CO)8<η², η²(CO)(CH=CHPh)2> (7), and Fe(CO)3<η⁴(CO)(CH=CHPh)2> (8), or solely complex 7 in which the ligand is bound in a η², μ-η², η², or η⁴ fashion.All three complexes have been fully characterized by X-ray crystallography.Crystal data for complex 6: C21H1 4FeO5, monoclinic, space group P2₁/n, a = 6.326(2) Angstroem, b = 14.567(2) Angstroem, c = 20.504(2) Angstroem, β = 96.91(2) deg, U = 1875(4) Angstroem³, D_c = 1.42 g cm^-3, Z = 4.For complex 7: C25H14Fe2O9, space group P1, a = 9.677(5) Angstroem, b = 10.635(5) Angstroem, c = 13.471(6) Angstroem, α = 104.24(3) deg, β = 105.46(4) deg, γ = 104.75(4) deg, U = 1216.7(8) Angstroem ³, D_c = 1.56 g cm^-3, Z = 2.For complex 8: C20H14FeO4, orthorhombic, space group Pbca, a = 13.397(2) Angstroem , b = 10.041(3) Angstroem, c = 26.579(2) Angstroem, U = 3575.1(8) Angstroem³, D_c = 1.39 g cm^-3, Z = 8.Upon reaction with MeLi under an atmosphere of CO, all of the three complexes each gave a mixture of the expected η⁴-ketene complex Fe(CO)4(η⁴-PhCH = CH(C=C=O)CH = CHPh) (9) as the result of a deoxygenation-carbonylation reaction, and the new μ-alkylidene complex Fe2(CO)6(μ-η³, η³-C(CH=CHPh)2) (10) as the result of a deoxygenation reaction of the starting complex followed by the trapping of the intermediate alkylidene complex by Fe(CO)3.Complex 10, C23H14Fe2O6, has been fully characterized by X-ray crystallography and shown to be orthorhombic, space group Pbcn, a = 17.155(4) Angstroem, b = 7.842(2) Angstroem, c = 15.857(2) Angstroem, U = 2133.2(5) Angstroem³, D_c = 1.55 g cm^-3, Z = 4.Keywords: Iron; Ketene; Alkylidene complexes; Dibenzylideneacetone