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Synthesis, Molecular Structure, and Physical Properties of the Complexes [{PhB(pz)₂(CH₂SMe)}₂M](M = MnII, FeII; pz = pyrazol-1-yl) Containing a Novel [N,N,S]-Heteroscorpionate Ligand

Title data

Reus, Christian ; Ruth, Kai ; Tüllmann, Sandor ; Bolte, Michael ; Lerner, Hans-Wolfram ; Weber, Birgit ; Holthausen, Max C. ; Wagner, Matthias:
Synthesis, Molecular Structure, and Physical Properties of the Complexes [{PhB(pz)₂(CH₂SMe)}₂M](M = MnII, FeII; pz = pyrazol-1-yl) Containing a Novel [N,N,S]-Heteroscorpionate Ligand.
In: European Journal of Inorganic Chemistry. Vol. 2011 (2011) Issue 11 . - pp. 1709-1718.
ISSN 1099-0682
DOI: https://doi.org/10.1002/ejic.201000552

Abstract in another language

Two transition metal complexes [L2M] {M = FeII (2), MnII (3)} of the novel [N,N,S] scorpionate ligand L = [PhB(pz)2(CH2SMe)]– have been synthesized and characterized by X-ray crystallography, magnetic measurements, cyclic voltammetry, and various spectroscopic techniques. In the solid state, both complexes 2 and 3 possess a distorted octahedral ligand sphere, but adopt different configurations (2: cis; 3: trans). According to X-ray diffraction data, Mössbauer spectroscopy, and SQUID measurements, compound 2 exists as low-spin complex in the solid state at temperatures T ≤ 20 °C (μeff ≈ 0.5 μB). Upon heating, the magnetic moment μeff increases continuously to a value of 1.8 μB at 90 °C, which indicates a temperature dependent high-spin ↔ low-spin transition above room temp. Solutions of 2 in CDCl3 showed paramagnetic behavior at 25 °C (μeff = 3.1 μB; Evans NMR method). Cyclic voltammetry (CH2Cl2, [Bu4N][PF6]; vs. FcH/FcH+) on 2 reveals a reversible FeII/FeIII redox transition at E1/2 = –0.16 V. Density functional theory (B3LYP-D/def2-TZVPP//B3LYP-D/SVP level) has been used to evaluate relative energies of the cis and trans isomers of 2 in their high-spin and low-spin states. Theoretical and experimental investigations have been extended to the related literature-known homoleptic FeII complexes [{PhB(pz)3}2Fe], [{PhB(pz)(CH2SMe)2}2Fe], and [{PhB(CH2SMe)3}2Fe]. The following order of ligand-field strengths has been established: [PhB(CH2SMe)3]– < [PhB(pz)(CH2SMe)2]– < [PhB(pz)2(CH2SMe)]– < [PhB(pz)3]–. The only significant deviation from this systematic behavior became evident for the unexpectedly low solution magnetic moment of [{PhB(CH2SMe)3}2Fe], which finds no parallel in the solid state. Computed spin-state splittings for the entire series of complexes, however, confirm the trend in solution magnetic moments and we relate the disaccording experimental observations to the presence of a second stereoisomer in crystals of [{PhB(CH2SMe)3}2Fe] which increases the paramagnetism of solid-state samples of this complex.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Anorganic Chemistry IV > Chair Anorganic Chemistry IV - Univ.-Prof. Dr. Birgit Weber
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Anorganic Chemistry IV
Result of work at the UBT: No
DDC Subjects: 500 Science > 540 Chemistry
Date Deposited: 27 Jul 2017 12:03
Last Modified: 27 Jul 2017 12:03
URI: https://eref.uni-bayreuth.de/id/eprint/38834