Iron(III) is a d5, paramagnetic metal center and its diethyl dithiocarbamate derivative, Fe(S2CN(CH2CH3)2)3, [Fe(Et2dtc)3], is soluble in deuterochloroform and gives a 1H NMR spectrum which was first reported about 50 years ago. It is the CH2 protons which are of interest; because of their proximity to the paramagnetic Fe(III), their signals in the NMR are shifted more than 30 ppm and show up as a somewhat broad signal. Two other iron(III) dithiocarbamate complexes, the dibenzyl derivative, Fe(S2CN(CH2C6H5)2)3, [Fe(Bz2dtc)3], and the morpholine derivative, Fe(S2CN(CH2)4O)3, [Fe(mordtc)3], are also paramagnetic and exhibit broadened signals in the 20-30 ppm range. Each of these three complexes exchange their dithiocarbamate ligands rapidly and mixing two of them in solution yields four complexes in statistical concentrations, e.g., mixing the diethyl and dibenzyl derivatives yields four complexes: Fe(S2CNEt2)3; Fe(S2CNEt2)2(S2CNBz2); Fe(S2CNEt2)(S2CNBz2)2; and Fe(S2CNBz2)3. Nickel(II) is d8 and diamagnetic. Its dibenzyldithiocarbamate derivative Ni(S2CN(CH2C6H5)2)2, [Ni(Bz2dtc)2], is soluble in deuterochloroform and exhibits signals in the 0-10 ppm range. Its dithiocarbamate ligands have been studied and do not rapidly exchange in solution. Mixing iron(III), and nickel (II) complexes, e.g., Fe(Et2dtc)3 and Ni(Bz2dtc)2 establishes a competition between the metals for these dithiocarbamates and allows the determination of their relative stability. Preliminary results indicate no significant preference in systems studied, although the exchange rate may be estimated from the results. This combination was studied during last year's research and the results were quite promising for a significant project. Once the exchanges of Ni(II) and Fe(III) are completed, thioseleno dithiocarbamates will be studied. This is continued research from last year, but using different compounds such as the nickel and the thioselenodithiocabamates.

Exchange between Fe(III) and Ni(II) dithiocarbamates in solution

249th National Meeting (2015)

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