Unprecedented pseudo-trigonal-bipyramidal intermediate-spin iron(III) complex: synthesis, crystal structure and magnetic properties of [Fe(4,4′-bipy)2(NCS)3]·(CH3)2CO

Abstract

The intermediate-spin five-co-ordinate complex [Fe(4,4′-bipy)₂(NCS)₃]·(CH₃)₂CO has been prepared, its structure determined and magnetic properties characterized. The structure is made up of mononuclear neutral species linked by van der Waals interactions. The co-ordination polyhedron is defined by five nitrogen atoms around the iron(III) ion in a distorted trigonal bipyramid. The three vertices of the equatorial plane are occupied by the thiocyanate ligands while the 4,4′-bipyridine ligands fill the axial positions. The Fe–N(CS) distances are 2.025(7), 2.04(2) and 2.02(2) Å and the axial Fe–N bond distances are 2.28(2) and 2.21(2) Å. The magnetic properties are consistent with an S = 3/2 ground state. The zero-field splitting in the ground state was found to be ca. 6 cm^–1. Variable temperature EPR spectra are briefly reported.