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Stabilization of High‐Valent Fe IV S 6 ‐Cores by Dithiocarbamate(1−) and 1,2‐Dithiolate(2−) Ligands in Octahedral [Fe IV (Et 2 dtc) 3− n (mnt) n ] ( n −1)− Complexes ( n =0, 1, 2, 3): A Spectroscopic and Density Functional Theory Computational Study
Author(s) -
Milsmann Carsten,
Sproules Stephen,
Bill Eckhard,
Weyhermüller Thomas,
George Serena DeBeer,
Wieghardt Karl
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200903381
Subject(s) - cyclam , dithiocarbamate , x ray absorption spectroscopy , chemistry , octahedron , crystallography , mössbauer spectroscopy , ligand (biochemistry) , electronic structure , absorption spectroscopy , spin states , oxidation state , ligand field theory , metal , inorganic chemistry , ion , crystal structure , computational chemistry , physics , biochemistry , receptor , organic chemistry , quantum mechanics
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 π 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.