Simple dithiocarbamate complexes

Although transesterification and transamidation reactions of simple carbonyl ligands are usually associated with the involvement of a co-ordinated nucleophile, there are some well-documented processes which unambiguously involve attack by an external nucleophile upon a co-ordinated electrophile. Dithiocarbamate complexes contain a chelated. S, 5"-bonded dithioamide ligand and undergo facile transamination reactions upon treatment of the copper complexes with amines (Fig. 3-22). 

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. 

Dithiocarbamates have been prepared from a wide range of amino acids (Fig. 20) (119-123). They are usually generated as the barium salts upon addition of barium hydroxide to the amino acid in the presence of carbon disulfide. Macias et al. (124) measured the ionization energies of various a-amino acid dithiocarbamates by X-ray photoelectron spectroscopy (XPS) and find that they increase as the side chain becomes longer probably being related to the change in donor ability. They react with transition metal salts to afford complexes in much the same way as simple dithiocarbamates (122, 125-138), although in some instances metal coordination of the carboxylate moiety is also proposed (119). 

Currently, the Cambridge Structural Database contains data for 1500 chelating dithiocarbamate ligands. Table III provides structural data for simple diethyldithiocarbamate complexes of aU the transition metals (where available). 

Tris(dithiocarbamate) complexes are readily oxidized (see below), however, upon addition of iodine only simple adducts, [Co(S2CNR2)3].2l2 (R = Me, Et R2 = C5H10, C4HgO), result. The dimethyldithiocarbamate complex has been... 

Both 2,2 -bpy, 1,10-phen, and their derivatives bind to both zinc (551, 591, 1158, 1906-1909, 1914, 1918, 1919, 1923, 1936-1939) and cadmium (1924-1930) in a bidentate manner leading to the generation of six-coordinate centers, with a distorted octahedral geometry. An elongation of the zinc-sulfur bonds by 0.2 A when compared to simple bis(dithiocarbamate) complexes is probably due to steric rather than electronic factors (1906), although binding of the base does result in an increase of electron density on zinc as shown by electrochemical and XPS studies (551, 552). 

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