The hexakis(thiocyanato)ferrate(III) ion: A coordination chemistry classic reveals an interesting geometry pattern for the thiocyanate ligands

Abstract

(NMe4)3[Fe(NCS)6] crystallizes from ethanol in the monoclinic space group C2/c. Two different types of complex ions are contained in the unit cell, though both possess exclusively N-coordination of the thiocyanate ligands. In one ion, the thiocyanate ligands are all essentially linearly bound, with an Fe-N-C angle of 174±4°, while in the other, there are two cis-thiocyanate ligands with a notably small Fe-N-C angle of 146.5°. The EPR and Mössbauer results show that all the iron(III) centers maintain the high-spin state down to 80 K, while the magnetic susceptibility confirms this to 2 K. Infrared and Mössbauer spectra provide evidence for an unusually "soft" lattice. Traditional criteria for interpretation of the infrared frequencies are not strictly applicable for this compound. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.