Variable-temperature magnetic-susceptibility measurements of spin equilibria for iron(III) dithiocarbamates in solution

Abstract

The magnetic moments of four tris(NN-disubstituted dithiocarbamato)iron(III) complexes have been measured in solution over a wide temperature range, using an n.m.r. method. The assumption of a simple Boltzmann distribution between high- and low-spin forms (⁶A₁ and ²T₂) gives a good fit to the observed susceptibility data. ΔS is approximately constant at ca. 20 J K^–1 mol^–1. Solvent effects are small and there is no evidence that hydrogen bonding to chloroform is important in solution. The paramagnetic shifts in the ¹H n.m.r. spectrum of one complex as a function of temperature have been analysed and give thermodynamic parameters in good agreement with those obtained from the susceptibility measurements.