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Variation of the Molecular and Electronic Structures of μ ‐Oxo Diferric Complexes with the Bridging Motive
Author(s) -
Zimmermann Thomas Philipp,
Limpke Thomas,
Stammler Anja,
Bögge Hartmut,
Walleck Stephan,
Glaser Thorsten
Publication year - 2018
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201800093
Subject(s) - chemistry , crystallography , mössbauer spectroscopy , quadrupole splitting , ligand (biochemistry) , covalent bond , dissolution , bridging ligand , infrared spectroscopy , stereochemistry , crystal structure , organic chemistry , biochemistry , receptor
The complexes [(susan){Fe III (OAc)( μ ‐O)Fe III (OAc)}](ClO 4 ) 2 , [(susan){Fe III ( μ ‐O)( μ ‐OAc)Fe III }](ClO 4 ) 3 , and [(susan){Fe III ( μ ‐O)( μ ‐CO 3 )Fe III }](ClO 4 ) 2 (susan = 4,7‐dimethyl‐1,1,10,10‐tetra(2‐pyridylmethyl)‐1,4,7,10‐tetraazadecane) were synthesized and characterized. Prominent IR vibrations do not shift from the solid state to CH 3 CN solutions demonstrating dissolution without structural rearrangements or substitutions. The acetates in [(susan){Fe III (OAc)( μ ‐O)Fe III (OAc)}] 2+ are in a trans conformation resulting in a C 2 symmetry of the central core and the overall complex. On the other hand, a second bridging ligand enforces a C S symmetry of the central core, which is incommensurable with the wrapping of the ligand around the central core resulting in only overall C 1 symmetry. The Fe–O Ac bonds are shorter for the terminal acetates (1.93 Å) than for the bridging acetate (1.97 and 2.07 Å). The bridging dianionic carbonate also results in shorter Fe–O carb bonds (1.91 and 1.97 Å). Mössbauer spectroscopy shows a lower quadrupole splitting for [(susan){Fe III ( μ ‐O)( μ ‐CO 3 )Fe III }](ClO 4 ) 2 in line with the shorter and thus more covalent Fe–O carb bonds. UV/Vis/NIR spectra differ in the d–d and in the LMCT regions for the mono‐ and doubly‐bridged complexes. The electrochemical characterization shows variations for the potentials for oxidations and reductions. This variation is discussed in light of the difference in π ‐donor interactions and the overall charge of the complexes.