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

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• 作者：Jay J. Dunsford ; David J. Evans ; Thomas Pugh ; Sachin N. Shah ; Nicholas F. Chilton ; Michael J. Ingleson
• 刊名：Organometallics
• 出版年：2016
• 出版时间：April 25, 2016
• 年：2016
• 卷：35
• 期：8
• 页码：1098-1106
• 全文大小：580K
• 年卷期：0
• ISSN：1520-6041

文摘

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 1–6 have been analyzed by ¹H NMR spectroscopy, X-ray crystallography, elemental microanalysis, Mössbauer spectroscopy (for 1 and 3–5), 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.