Iron complexes dithiocarbamates

The EPR spectrum of a spin-equilibrium complex can be used to establish a lower limit to the spin state lifetimes of the order of 10 10 second. In an important paper in 1976, Hall and Hendrickson reported observation of EPR signals for both the high-spin and the low-spin isomers of iron(III) dithiocarbamate complexes at 4 12 K as powders, glasses, and doped solids (71). This resolved the question whether these complexes possess distinct high-spin and low-spin states. It also sets a lower limit on their interconversion lifetimes. Similarly, the observation of signals for both the high-spin and low-spin states of [Co(terpy)22+] (97) leads to the same conclusions about this complex. In both cases the interconversion rates in solution have proved too fast to measure, with lifetimes of less than 10-9 second indicated. The solution measurements were undertaken, of course, at room temperature and the EPR measurements at close to 4 K. Significant differences in the rates of solid and solutions at room temperature are still possible. 

The traditional copper fungicides are in fact inorganic copper coordination compounds The still most important group of organic protectant fungicides, the dithiocarbamates, are applied in the form of their metal-coordination compounds. Dimethyldithiocarbamate as the iron complex ferbam and the zinc complex ziram, ethylenebisthiocarbamate as the zinc complex zineb and the manganese complex maneb. 

As previously noted, spin cross-over behaviour is well established in iron(II) complexes and there are also examples involving iron(III) species. For example, a variety of iron(III) dithiocarbamate complexes of the type [Fe(S2CNR2)3j having a trigonally distorted octahedral geometry display high-spin/low-spin cross-over behviour 49,50 Little is known about the spin forbidden d-d transitions of iron(III) complexes due to near-UV charge transfer bands that tail into the visible part of the spectrum. Even simple iron(III) salts in aqueous media are yellow. 

SYNONYMS carbamate, dimethylcarbamodithioic acid, iron complex, ferric dimethyl-dithiocarbamate, iron dimethyldithiocarbamate, iron tris (dimethyldithiocarbamate), karbam... 

Iridium(V) complexes, 1158 fluorides, 1158 Iridium(VI) complexes, 1158 Iron complexes acetonitrile, 1210 analysis, 1180, biological systems, 1180 coordination geometries, 1183 coordination numbers, 1182-1187 dinitrosyldicarbonyl, 1188 Mdssbauer spectroscopy, 1181 nitric oxide, 1187-1195 nitrosyls binary, 1188 bis(dithiolene), 1193 carbonyl, 1188 dithiocarbamates, 1192 halides, 1193 iodide, 1193... 

The most stable iron(IV) species seem to be those containing dithiocarbamate or related ligands such as the low-spin cationic iron tris (dithiocarbamate) complex obtained by oxidation of the neutral iron(III) parent (the high-spin air-sensitive iron(II) anion is also available by reduction) [100]. 

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