title: Stabilization of high-valent Fe(IV)S6-cores by dithiocarbamate(1-) and 1,2-dithiolate(2-) ligands in octahedral [Fe(IV)(Et2dtc)(3-n)(mnt)(n)]((n-1)-) complexes (n=0, 1, 2, 3): a spectroscopic and density functional theory computational study.
abstract: A detailed spectroscopic and quantum chemical analysis is presented to elucidate the electronic structures of the octahedral complexes [Fe(Et(2)dtc)(3-n)(mnt)(n)](n-) (1-4, n=3, 2, 1, 0) and their one-electron oxidized analogues [Fe(Et(2)dtc)(3-n)(mnt)(n)]((n-1)-) (1(ox)-4(ox)); (mnt)(2-) represents maleonitriledithiolate(2-) and (Et(2)dtc)(1-) is the diethyldithiocarbamato(1-) ligand. By using X-ray crystallography, Mössbauer spectroscopy, and Fe and S K-edge X-ray absorption spectroscopy (XAS) it is convincingly shown that, in contrast to our previous studies on [Fe(cyclam)(mnt)](1+) (cyclam=1,4,8,11-tetraazacyclotetradecane), the oxidation of 1-4 is metal-centered yielding the genuine Fe(IV) complexes 1(ox)-4(ox). For the latter complexes, a spin ground state of S=1 has been established by magnetic susceptibility measurements, which indicates a low-spin d(4) configuration. DFT calculations at the B3LYP level support this electronic structure and exclude the presence of a ligand pi radical coordinated to an intermediate-spin ferric ion. Mössbauer parameters and XAS spectra have been calculated to calibrate our computational results against the experiment. Finally, a simple ligand-field approach is presented to correlate the structural features obtained from X-ray crystallography (100 K) with the spectroscopic data.
authors.affiliation: Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36,D-45470 Mülheim an der Ruhr, Germany.
authors.forename: Carsten
authors.initials: C
authors.lastname: Milsmann
authors.forename: Stephen
authors.initials: S
authors.lastname: Sproules
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.forename: Thomas
authors.initials: T
authors.lastname: Weyhermüller
authors.forename: Serena DeBeer
authors.initials: SD
authors.lastname: George
authors.forename: Karl
authors.initials: K
authors.lastname: Wieghardt
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D055664:Electrochemical Techniques; D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D008968:Molecular Conformation; D010084:Oxidation-Reduction; D015204:Spectroscopy, Mossbauer; D013438:Sulfhydryl Compounds / Q000737:chemistry; D056928:X-Ray Absorption Spectroscopy
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D013438:Sulfhydryl Compounds; C459462:maleinitriledithiolate; D007501:Iron