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

The intermediate-spin five-co-ordinate complex [Fe(4,4'-bipy)(2)(NCS)(3)].(CH3)(2)CO 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 live 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) Angstrom and the axial Fe-N bond distances are 2.28(2) and 2.21(2) Angstrom. 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.