On the anomalous magnetic properties of tris(diselenocarbamato)iron(III) compounds

Abstract

An extended magnetic investigation of a series of pseudo-octahedral [Fe(Se₂CNR₂)₃] compounds [R₂= piperidino, morpholino, thiomorpholino, Bu₂, Et₂, (PhCH₂)₂, (C₆H₁₃)₂, and MePh] has been made at 90–400 K. Diamagnetic compounds not containing iron, Se(Se₂CNEt₂)₂, Se[Se₂CN(CH₂Ph)₂]₂, and (Se₂CNMePh)₂, have also been isolated and their presence could explain the previously reported low-spin classification of [Fe(Se₂CNR₂)₃] compounds. The reported measurements demonstrate that the magnetic behaviour of these compounds is anomalous, the µ values generally ranging between the limiting values typical for ⁶A₁ and ²T₂ states. Treatment of the experimental values by means of van Vleck's equation has enabled the evaluation of the crossover parameters, and a full comparison with the dithiocarbamate derivatives is made. The influence of the substituents on the nitrogen of the ligand on the position of the spin equilibrium is discussed.