Steffen Meyer, C. Orben, S. Demeshko
Nov 17, 2011
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Organometallics
Abstract
A series of new and known bis(imidazolium) chloride and bromide salts bridged by either a methylene group (1–8, 10a,b) or an ethylene group (9a,b) and bearing different N substituents (Me, Et, Bn, tBu, Mes) have been reacted with [Fe{N(SiMe3)2}2]2 to yield the four-coordinate iron(II) complexes [LFeX2] (11–20; X = Cl, Br; L = chelating bis(imidazolylidene) ligand). Molecular structures of six of these complexes have been characterized by X-ray crystallography, and selected examples have been characterized by 1H NMR and UV–vis spectroscopy, cyclic voltammetry, Mossbauer spectroscopy, and SQUID magnetometry. In all cases the iron(II) is found in a distorted-tetrahedral environment; it is in the high-spin state and shows large quadrupole splittings in the range 3.67–4.03 mm·s–1 (δ = 0.73–0.81 mm·s–1). Subtleties of the metric parameters depend on the bridging unit between the two imidazolylidene groups, the peripheral N substituents, and the coligand (Cl or Br). In case of rather small (Me, Et) or flexible (...