Mössbauer-Effect Study of Some Iron(III) N,N-Dialkyldithiocarbamates

Abstract

A Mössbauer‐effect study has been carried out for ⁵⁷Fe in a series of iron (III) N,N–dialkyldithiocarbamates, in which a ferric ion is octahedrally coordinated to six sulfur atoms. All the compounds showed a single spectrum at 300°K so that the rate of exchange between the high‐spin and low‐spin states must be greater than 10⁷ sec^− 1, and there was a large increase in resonant absorption on cooling to 77°K. The isomer shifts were large for covalent ferric ions (∼ + 0.4 mm sec^− 1 with respect to iron at room temperature) and suggest that the metal s electrons are screened from the nucleus by electron donation from the ligands. Iron (III) pyrrolidyldithiocarbamate $\mathrm{(S\hspace{0.17em}=\hspace{0.17em}}\frac{5}{2})$ has long electron spin relaxation times at 4.2°K and its spectrumshows a hyperfine field of 430 kG and a small quadrupole splitting $[\frac{1}{2}{\mathrm{(e}}^2\text{Qq)\hspace{0.17em}=\hspace{0.17em}0.20}{\mathrm{mm\; sec}}^{\text{−1}}]$ which results from an elongated distortion. The other compounds studied show relaxation effects though with shorter times, and have larger and more temperature‐dependent quadrupole splittings (∼0.78 mm sec^− 1 at 4.2°K). The decrease in quadrupole splitting observed as the temperature increases is partly due to the increasing population of the ${}^6{A}_1$ state. Spectra in magnetic fields show the electric field gradient to be positive and perpendicular to the axis of magnetization.