Three-coordinate iron(II) expanded ring N-heterocyclic carbene complexes

Dunsford, Jay J.; Evans, David J.; Pugh, Thomas; Shah, Sachin N.; Chilton, Nicholas F.; Ingleson, Michael J.

Abstract

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)X 2 ] (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)Br 2 (THF)] (3) or [Fe(NHC)Br 2 ] (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)Br 2 (THF)] (6) (NHC = SDiPP), again dependent upon the solvent of recrystallization. Compounds 1-6 have been analyzed by 1 H 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.

Citation

Dunsford, J. J., Evans, D. J., Pugh, T., Shah, S. N., Chilton, N. F., & Ingleson, M. J. (2016). Three-coordinate iron(II) expanded ring N-heterocyclic carbene complexes. Organometallics, 35(8), 1098-1106. https://doi.org/10.1021/acs.organomet.6b00121

• Acceptance Date: Apr 5, 2016
• Online Publication Date: Apr 14, 2016
• Publication Date: May 9, 2016
• Deposit Date: Apr 11, 2016
• Publicly Available Date: Apr 14, 2016
• Journal: Organometallics
• Print ISSN: 0276-7333
• Electronic ISSN: 1520-6041
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 35
• Issue: 8
• Pages: 1098-1106
• DOI: https://doi.org/10.1021/acs.organomet.6b00121
• Keywords: N-heterocyclic carbene complexes
• Public URL: https://hull-repository.worktribe.com/output/435559
• Publisher URL: http://pubs.acs.org/doi/abs/10.1021/acs.organomet.6b00121
• Additional Information: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Organometallics, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.organomet.6b00121