Iron complexes of terdentate nitrogen ligands: formation and X-ray structure of three new dicationic complexes
Graphical abstract
The synthesis and X-ray structure of the iron complexes (L1 = 6,6″-di(p-tolyl)-2,2′:6′,2″-terpyridine and L2 = 2,6-bis-(3-mesitylpyrazol-1-yl)pyridine) are presented. (L1)2Fe2+ was shown to be a high-spin complex, whereas (L2)2Fe2+ was low-spin.
Introduction
It has been shown recently that binding 2,6-bis(imino)-pyridyl ligands to iron chlorides leads to five-coordinate complexes that behave as highly efficient catalysts for the polymerization and oligomerization of ethylene, in the presence of a suitable activator [1]. However, subsequent searches for further terdentate ligands inducing similar properties revealed much less positive [2]. In this context, we describe here our studies on the coordination of two N3 donor ligands to iron.
Section snippets
Results and discussion
The ligand 6,6″-di(p-tolyl)-2,2′:6′,2″-terpyridine (L1, Scheme 1) was best synthesized by a variation of the Kröhnke methodology [3]. Instead of the classical Manich salt, the neutral diamine 2,6-bis(3-dimethylamino-1-oxopropyl-2-ene)pyridine was first obtained in good yield from the reaction of 2,6-diacetylpyridine with two equiv. of N,N-dimethylformamide dimethyl acetal in DMF [4]. It was then reacted with two equiv. of the potassium salt of p-Me-acetophenone in THF, before addition of
General
As the inorganic compounds described herein are air-sensitive, all experiments were performed in a glove box under controlled nitrogen atmosphere. THF, diethyl ether, pentane were dried over Na-benzophenone and acetonitrile over CaH2 before distillation under nitrogen. Anhydrous FeCl2 (Strem) and FeCl3 were used as purchased. Ligand L2 was synthesized according to procedures described previously in the literature [8]. 1H NMR spectra were recorded on Bruker AC-200 or Avance-300 spectrometers at
Supplementary material
Crystallographic data for structural analysis have been deposited with the Cambridge Crystallographic Data Centre, CCDC Nos. 203433, 203434, 203435 for (C58H58Cl4Fe2N10) , (C58H46Cl8Fe3N6) and (C74H90Cl8Fe3N10O4) , respectively. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road,
Acknowledgements
We are grateful to Mrs. Michelle Martigneaux from the Service Commun NMR and Caroline Dietrich-Schneider from the Service de Spectrométrie de Masse at the University Louis Pasteur Strasbourg.
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