Transition metals, dithiocarbamate complexes tris

Abstract - The temperature dependence of the proton nmr spectra of dithiocarbamato iron(III) complexes is markedly solvent dependent. A study is made of the temperature dependence of the nmr shifts for the N-CH2 protons in tris(N,N-dibutyldithiocar-bamato) iron(III) in acetone, benzene, carbon disulfide, chloroform, dimethyIformamide, pyridine and some mixed solvents. This contribution shall outline first how the nmr shifts may be interpreted in terms of the Fermi contact interaction and the dipolar term in the multipole expansion of the interaction of the electron orbital angular momentum and the electron spin dipol-nuclear spin angular momentum. This analysis yields a direct measure of the effect of the solvent system on the environment of the transition metal ion. The results are analysed in terms of the crystal field environment of the transition metal ion with contributions from (a) the dithiocarbamate ligand (b) the solvent molecules and (c) the interaction of the effective dipole moment of the polar solvent molecule with the transition metal ion complex. The model yields not only an explanation for the unusual nmr results but gives an insight into the solvent-solute interactions in such systems. 

In this paper we shall extend our earlier interpretation of the redox results to the nmr data for the N - CH2 protons in tris(N,N-diethyldithiocarbamato) iron(III). We shall show that the solvent dependence of the nmr shifts can be interpreted as arising from solvent interactions with the iron(III) dithiocarbamate system. Although the solvent interactions are small compared with the electronic interactions within the transition metal iron complex the effect is marked since in these cases for the d iron system there are low lying electronic states where the energy separation is sensitive to small changes in the crystal field environment of the transition metal ion. 

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