Sterically Encumbered Coordination Sites. Iron(II) Complexes of Jäger‐type ligands with a Terphenyl Backbone

Abstract

Dedicated to Professor Josef Breu on the Occasion of his 60 th BirthdayA Schiff base-like ligand H 2 L TerPh featuring a para-terphenyl backbone was synthesized and converted in two steps to an octahedral iron(II) coordination polymer with 1,2-bis-(4-pyridyl)ethylene as bridging ligand. Single crystal X-ray structure analysis was possible for the free ligand and the two octahedral iron(II) complexes. The Schiff base-like ligand features a [N 2 O 2 ] 2À coordination sphere for the metal center and the paraterphenyl backbone introduces intrinsic steric constraint. Char-acterization of the coordination polymer with an N 4 O 2 coordination sphere around the iron center via magnetic measurements (SQUID) and room temperature Mössbauer spectroscopy revealed HS character in the entire temperature range investigated. Structure modelling with DFT calculations supports the findings, but support also the possibility of spin crossover in solution.

Synthesis and crystal structures of three Schiff bases derived from 3-formylacetylacetone and benzyl-, tert-butyl- and (S)-methylbenzylamine

“…successfully used the deprotonation of 3-aminomethylenepentane-2,4-dione type Schiff bases to generate -iminoenolate chelate ligands, with special focus on tetradentate salen-type ligands (Wolf & Ja ¨ger, 1966). In particular, these salen-type ligands have found broad application in the synthesis of Fe II complexes exhibiting spin-crossover effects (Du ¨rrmann et al, 2021). Moreover, the coordination properties of the iminoenolate ligands are conveniently modified by the introduction of additional donor groups.…”