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Z. Naturforsch. 2014,
69b, 1206 – 1214
doi:10.5560/ZNB.2014-4176
N-Donor Competition in Iron Bis(chelate) Bis(pyrazolyl)pyridinylmethane Complexes
1 Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr. 5–13, 81377 München, Germany
2 Universität Bayreuth, Anorganische Chemie II, Universitätsstraße 30, NW I, 95440 Bayreuth, Germany
Reprint requests to Prof. Dr. S. Herres-Pawlis. Fax: 089-218077904. E-mail:
sonja.herres-pawlis@cup.uni-muenchen.de
Received August 5, 2014 / published online December 19, 2014
Dedicated to Professor Hubert Schmidbaur on the occasion of his 80th birthday
We report on the synthesis and structural characterisation of the bis(chelate) bis(pyrazolyl)pyridinylmethane iron(II) complexes [Fe{HC(Pz)2(Py)}2][CF3CO2]2, [Fe{HC(3-iPrPz)(5-iPrPz)(Py)}2][CF3SO3]2 and [Fe{HC(3-iPrPz)(5-iPrPz)(Py)}2][FeBr4]Br·2C4H8O. During the synthesis of the latter ones, an isomerisation of the ligand is observed: the pyrazolyl substituent formally moves from the 3 to the 5 position. Since the donor competition between pyrazolyl and pyridinyl moieties is important for the coordination properties, we also studied the donor properties by density functional theory and natural
bond orbital analysis (NBO). As a result, the pyridinyl donor is generally weaker than the pyrazolyl donor, but the pyrazolyl donor is heavily influenced by the alkyl substitution pattern. To confirm the low-spin state of the complexes, magnetic susceptibility measurements have been performed.
Key words: Iron, Bis(pyrazolyl)methane Complexes, X-Ray Crystallography, DFT, NBO