Please use this identifier to cite or link to this item: http://dx.doi.org/10.14279/depositonce-5482
Main Title: Controlled ligand distortion and its consequences for structure, symmetry, conformation and spin-state preferences of iron(II) complexes
Author(s): Kroll, Nicole
Theilacker, Kolja
Schoknecht, Marc
Baabe, Dirk
Wiedemann, Dennis
Kaupp, Martin
Grohmann, Andreas
Hörner, Gerald
Type: Article
Language Code: en
Abstract: The ligand-field strength in metal complexes of polydentate ligands depends critically on how the ligand backbone places the donor atoms in three-dimensional space. Distortions from regular coordination geometries are often observed. In this work, we study the isolated effect of ligand-sphere distortion by means of two structurally related pentadentate ligands of identical donor set, in the solid state (X-ray diffraction, Fe-57-Mossbauer spectroscopy), in solution (NMR spectroscopy, UV/Vis spectroscopy, conductometry), and with quantum-chemical methods. Crystal structures of hexacoordinate iron(II) and nickel(II) complexes derived from the cyclic ligand L-1 (6-methyl-6-(pyridin-2-yl)-1,4-bis(pyridin-2-ylmethyl)-1,4-diazepane) and its open-chain congener L-2 (N-1,N-3,2-trimethyl-2-(pyridine-2-yl)-N-1,N-3-bis(pyridine-2-ylmethyl) propane-1,3-diamine) reveal distinctly different donor set distortions reflecting the differences in ligand topology. Distortion from regular octahedral geometry is minor for complexes of ligand L-2, but becomes significant in the complexes of the cyclic ligand L-1, where trans elongation of Fe-N bonds cannot be compensated by the rigid ligand backbone. This provokes trigonal twisting of the ligand field. This distortion causes the metal ion in complexes of L-1 to experience a significantly weaker ligand field than in the complexes of L-2, which are more regular. The reduced ligand-field strength in complexes of L-1 translates into a marked preference for the electronic high-spin state, the emergence of conformational isomers, and massively enhanced lability with respect to ligand exchange and oxidation of the central ion. Accordingly, oxoiron(IV) species derived from L-1 and L-2 differ in their spectroscopic properties and their chemical reactivity.
URI: http://depositonce.tu-berlin.de/handle/11303/5889
http://dx.doi.org/10.14279/depositonce-5482
Issue Date: 2015
Date Available: 13-Sep-2016
DDC Class: 540 Chemie
Sponsor/Funder: DFG, EXC 314, Unifying Concepts in Catalysis
Creative Commons License: https://creativecommons.org/licenses/by/3.0/
Journal Title: Dalton transactions : a journal of inorganic chemistry, including bioinorganic, organometallic, and solid-state chemistry / Royal Society of Chemistry
Publisher: Royal Society of Chemistry
Publisher Place: Cambridge
Volume: 44
Issue: 44
Publisher DOI: 10.1039/c5dt02502h
Page Start: 19232
Page End: 19247
EISSN: 1477-9234
ISSN: 1477-9226
Appears in Collections:Unifying Concepts in Catalysis (UniCat) » Publications
Fachgebiet Anorganische Chemie - Festkörper- und Materialchemie » Publications

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