om6b00121_si_001.pdf (1.07 MB)

Three-Coordinate Iron(II) Expanded Ring N‑Heterocyclic Carbene Complexes

Download (1.07 MB)
journal contribution
posted on 14.04.2016 by Jay J. Dunsford, David J. Evans, Thomas Pugh, Sachin N. Shah, Nicholas F. Chilton, Michael J. Ingleson
A sterically demanding seven-membered expanded ring N-heterocyclic carbene (NHC) ligand allows access to rare examples of three-coordinate iron­(II)–NHC complexes incorporating only halide coligands of the general formula [Fe­(NHC)­X2] (NHC = 7-DiPP; X = Br (1) Cl (2)). Reducing the steric influence of the ancillary NHC ligand through modulation of the N-aryl substituents leads to either four- or three-coordinate complexes of the general formula [Fe­(NHC)­Br2(THF)] (3) or [Fe­(NHC)­Br2] (4) (NHC = 7-Mes), dependent upon the solvent of recrystallization. The further reduction of NHC steric influence results in four-coordinate geometries at iron in the form of the dimeric species [Fe­(NHC)­Br­(μ-Br)]2 (5) or [Fe­(NHC)­Br2(THF)] (6) (NHC = SDiPP), again dependent upon the solvent of recrystallization. Compounds 16 have been analyzed by 1H NMR spectroscopy, X-ray crystallography, elemental microanalysis, Mössbauer spectroscopy (for 1 and 35), and Evans method magnetic susceptibility. In addition to these measurements the three-coordinate species 1 and 4 have been further analyzed by SQUID magnetometry and CASSCF calculations, which show significant magnetic anisotropy that is extremely sensitive to the coordination geometry.