Abstract

The present study aims to synthesis and full characterization of two new pentacoordinated isothiocyanate iron(III) mixed ligand complexes featuring dianionic (N2O2)(2-) tetradentate Schiff-base ligands unsymmetrically substituted by either a pair of acceptor (4-fluorophenyl and nitro) or donor (ferrocenyl and methoxy) substituents. The two neutral complexes 3 and 4 were prepared in very good yields (similar to 90 %) upon reaction of their respective chloro-iron(III) precursors 1 and 2 with sodium thiocyanate in refluxing ethanol. The two paramagnetic compounds 3 and 4 were characterized by elemental analysis, FT-IR and UV-vis spectroscopy, and mass spectrometry. The stretching frequencies of the thiocyanate group observed at 2014 and 2062 cm(-1), respectively, indicate a N-bonded NCS- moiety, in agreement with the HSAB principle. The crystal structure of 3 revealed that in the five-coordinate monomer, the iron atom adopts a slightly distorted square-pyramidal geometry, with the N and O atoms of the Schiff-base ligand occupying the basal sites and the nitrogen atom of the isothiocyanate co-ligand located at the apex of the pyramid. Intermolecular interactions in complex 3 have been addressed with the aid of Hirshfeld surface analysis as well as fingerprint plots. Magnetic susceptibility measurements (2-300 K) showed a high-spin configuration (S = 5/2) for the d(5) Fe(III) ion in 3. (C) 2021 Elsevier B.V. All rights reserved.