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Updated: Jan 11, 2026

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses
Published on: June 7, 2018
A Combined Magnetic and Mössbauer Spectroscopic Study of High-Spin Half-Sandwich Fe(I) Complexes in Monomeric and
Katharina Münster1, Dirk Baabe1, Jan Raeder1
1Institut für Anorganische Und Analytische Chemie, Technische Universität Braunschweig, Braunschweig 38106, Germany.
Abstract:
The reduction of the iron(II) half-sandwich precursors [Cp'FeN(R)(SiMe3)] (R = SiMe3, 2,6-di-iso-propylphenyl (dipp)) with KC8 yields the one-dimensional polymeric iron(I) complexes {[Cp'Fe(N(SiMe3)3)]K}n (4) and {[Cp'Fe(N(dipp)(SiMe3))]K}n (5). Addition of 18-crown-6 breaks up these chains and affords the monomeric salts [Cp'Fe(N(SiMe3)2)][K(18-crown-6)(thf)2] (6) and [Cp'Fe(N(dipp)(SiMe3))][K(18-crown-6)(thf)2] (7). All four compounds were structurally characterized by single-crystal X-ray diffraction analysis and adopt an S = 3/2 spin ground state. Zero-field 57Fe Mössbauer spectra uncover slow magnetic relaxation at low temperatures in each complex. Complementary CASSCF/NEVPT2 calculations reveal an S = 3/2 ground-state Kramers doublet that is ca. 100 cm-1 below the first excited state. These findings are confirmed by results from DC susceptibility and magnetization experiments. The slow relaxation of magnetization is further characterized via AC susceptibility measurements, unveiling detectable slow relaxation of magnetization at zero external field for 4-6. Complex 4 exhibits an unusual field dependence of the quantum tunneling of magnetization, akin to exchange-bias effects, which are commonly observed in lanthanide dimers.
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