Iron(III) Half-Sandwich Complexes of the Two-Legged Piano-Stool [CpFe(aryl)Cl] Type from the Corresponding Aryliron(II) Precursors

Abstract

Instead of reacting with the σ-mesityliron(II) complex [Cp′′′Fe(σ-C6H2Me3-2,4,6)] (1; Cp′′′ = 1,2,4-tri-tert-butylcyclopentadienyl) to form a cyclohexadienyl(cyclopentadienyl)iron(II) sandwich complex with palladium coordination to the ipso carbon atom of the six-membered ring, palladium(II) chloride oxidized 1 to the mesityliron(III) complex [Cp′′′Fe(σ-C6H2Me3-2,4,6)Cl] (5) with a two-legged piano-stool geometry. The oxidation of [4CpFe(σ-C6H2Me3-2,4,6)] (4;4Cp = tetraisopropylcyclopentadienyl) to [4CpFe(σ-C6H2Me3-2,4,6)Cl] (6) was accomplished with hexachloroethane. Two other derivatives, [4CpFe(σ-C6H3iPr2-2,6)Cl] (7) and [5CpFe(σ-C6H3iPr2-2,6)Cl] (8;5Cp = pentaisopropylcyclopentadienyl), could also be obtained by the same method. The molecular structures of 5 and 6 are compared with the structure of the (tetraisopropylcyclopentadienyl)iron(III) dibromide [4CpFeBr2] (9), which was formed from the iron(II) analogue [4CpFe(µ-Br)]2during attempted nucleophilic substitution with an arylmagnesium bromide.