High‐Spin Cyclopentadienyl Complexes: A Single‐Molecule Magnet Based on the Aryl‐Iron(II) Cyclopentadienyl Type

Magnetic anisotropy in two- to eight-coordinated transition–metal complexes: Recent developments in molecular magnetism

“…A high-spin cyclopentadienyl iron(II) organometallic complex with the formula [ 5 CpFe(C 6 H 3 i Pr-2,6)] was obtained by reacting the diamagnetic [ 5 CpFeBr(dme)] ( 5 Cp = C 5 iPr 5 ) with 2,6-diisopropylphenyl-1-magnesium bromide, as described by Weismann et al [32]. Formally, this complex has a linear shape but is not two-coordinated because cyclopentadienyl ligands are : 3 coordinating.…”

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

“…The Fe-C12 (C ipso ) bond [1.969(4) Å] is shorter than that (2.043 Å) of the aryliron(II) derivative 4 [10] (Scheme 2), as expected from the different ionic radii of highspin Fe II and Fe III ions. [11] The Fe III -C bonds in N-heterocyclic carbene complexes are even longer, for example, the Fe-CH 3 Scheme 3.…”

“…With a deviation of 4.8-5.4°from the ideal 180°angle between the Cp centroids and the ipso-carbon atom, complex 2 can be considered to have a structure similar to an umbrella, comparable to those of other (σ-aryl)(cyclopentadienyl)iron(II) complexes such as 1, [6] [ 4 CpFe(σ-C 6 H 3 iPr 2 -2,6)], [9] and [ 5 CpFe-(σ-C 6 H 3 iPr 2 -2,6)] ( 5 Cp = pentaisopropylcyclopentadienyl). [10] In an orienting experiment aiming at σ/π rearrangement with a palladium-based Lewis acid, the mesityl complex 1 was treated with palladium(II) chloride. From the black reaction solution, the redox product [Cp′′′Fe(σ-C 6 H 2 Me 3 -2,4,6)Cl] was obtained as a black oil, which was sparingly soluble in pentane and highly soluble in toluene or tetrahydrofuran (THF; Scheme 3).…”

“…The crystal structures were obtained by XRD measurements with a Stoe IPDS diffractometer (5) or an Oxford Diffraction Gemini Ultra diffractometer (others). The mass spectra were recorded with a [9] [ 5 CpFeBr(dme)] (dme = 1,2-dimethoxyethane), [10] mesitylmagnesium bromide, [16] mesityl(tri-tert-butylcyclopentadienyl)iron (1), [6] (2,6-diisopropylphenyl)magnesium bromide, [10] (2,6-diisopropylphenyl)(tetraisopropylcyclopentadienyl)iron (3), [8] and (2,6-diisopropylphenyl)-(pentaisopropylcyclopentadienyl)iron (4) [10] were synthesized according to literature procedures. Hexachloroethane (Acros, 99 %) was used as purchased.…”

“…Four paramagnetic (alkylcyclopentadienyl)(aryl)iron(II) complexes used as starting compounds: [Cp′′′Fe(σ-C 6 H 2 Me 3 -2,4,6)] (1), [6] [ 4 CpFe-(σ-C 6 H 2 Me 3 -2,4,6)] (2; this work), [ 4 CpFe(σ-C 6 H 3 iPr 2 -2,6)] (3), [9] [ 5 CpFe-(σ-C 6 H 3 iPr 2 -2,6)] (4). [10] As the σ-aryl complex 2 has not been described previously, we report its synthesis and discuss its molecular structure before we proceed to the oxidation of these iron(II) compounds.…”