Mercs, Laszlo Labat, Gaël Neels, Antonia Ehlers, Andreas Albrecht, Martin 2006-10-12 A series of new piano-stool iron(II) complexes comprising mono- and bidentate chelating <i>N</i>-heterocyclic carbene ligands [Fe(cp)(CO)(NHC)(L)]X have been prepared and analyzed by spectroscopic, electrochemical, crystallographic, and theoretical methods. Selectively substituting the L site with a series of ligands going from carbene to pyridine to CO suggests that CO is the strongest π acceptor, while the behavior of pyridine and carbene is nearly identical. This suggests that in these complexes comprising an electron-rich iron(cp)(carbene) fragment, <i>N</i>-heterocyclic carbenes are not pure σ donors but also moderate π acceptors. Theoretical calculations support this bonding model and indicate charge saturation at the metal as key for π back-bonding to <i>N</i>-heterocyclic carbenes. On the basis of voltammetric measurements, the Lever electrochemical parameter of these carbenes has been determined: <i>E</i>_L = +0.29. Systematic substitution of the wingtip groups of the carbene revealed only subtle changes in the electronic properties of the iron center, thus providing a suitable methodology for ligand-induced fine-tuning of the coordinated metal. application/pdf https://folia.unifr.ch/global/documents/300797 https://folia.unifr.ch/documents/300797/files/albrecht_psi.pdf https://folia.unifr.ch/documents/300797/files/albrecht_psi_sm.pdf https://folia.unifr.ch/documents/300797/files/albrecht_psi_sm1.tif https://folia.unifr.ch/documents/300797/files/albrecht_psi_sm2.tif https://folia.unifr.ch/documents/300797/files/albrecht_psi_sm3.tif https://folia.unifr.ch/documents/300797/files/albrecht_psi_sm4.tif https://folia.unifr.ch/documents/300797/files/albrecht_psi_sm5.tif https://folia.unifr.ch/documents/300797/files/albrecht_psi_sm6.tif https://folia.unifr.ch/documents/300797/files/albrecht_psi_sm3.cif eng info:eu-repo/semantics/altIdentifier/doi/10.1021/om060637c info:eu-repo/semantics/openAccess License undefined Organometallics. - 2006, vol. 25, no. 23, p. 5648 -5656 info:eu-repo/classification/udc/54 Piano-stool iron(ii) complexes as probes for the bonding of n-heterocyclic carbenes: indications for -acceptor ability http://purl.org/coar/resource_type/c_6501