Magnetic interactions in iron(III) bis(dithiocarbamates)

Further magnetic and structural studies have been made of the bis(N,N-diethyldithiocarbamato) iron(III)X complexes (X = Cl−, Br−, I−, SCN−). The I− homolog is antiferromagnetic (TN = 1.9 °K), while the SCN− derivative is a simple paramagnet (to 1.4 °K). The crystal structure of the paramagnetic bromo derivative was found to be nearly identical to that of the ferromagnetic chloro homolog. The different collective magnetic properties of the chloro and bromo homologs arise from combined exchange and uniaxial crystal field interactions. Using known crystal field parameters and a molecular field description of magnetic interactions, an effective intermolecular exchange constant of 0.12 ± 0.03 °K is derived. Exchange broadened paramagnetic resonance spectra are shown to correlate well with the collective magnetic behavior of the complexes. Solution proton NMR data are interpreted in terms of d-electron delocalization to the dithiocarbamate ligand π-type orbital system.