Dithiocarbamate complexes tris

Trivalent iron dithiocarbamate complexes have been extensively studied, because of the existence of "spin equilibria in these complexes. Table II outlines the tris(l,l-dithiocarbamate) iron(III) complexes and, some of their physical properties. 

Determinations of reduction potentials for a series of Fe(III) and Mn(III) tris-dithiocarbamate complexes by voltametry in the presence of various concentrations of polar molecules were conducted. The t y2 values varied linearly with the mole fraction of the particular polar molecule present (274). A theoretical model that was consistent with the experimentally derived f i/2 values was advanced. 

Despite the ambiguity regarding the assignment of formal oxidation states to metal and ligand in many dithiolate complexes, the structure and properties of the benzyltriphenylphosphonium salt of tris(l,l-dicarboethoxyethylene-2,2-dithiolato)ferrate [BzPh3P]2[Fe(DED)3] (DED = structure 139) are considered486 to be best described in terms of an Fe,v complex. The structure is close in important details to that of the dithiocarbamate complex described above.485... 

Certain tris(dithiocarbamate) complexes constitute well-studied examples of spin-crossover equilibria, as discussed elsewhere (page 567), but the ethyl xanthate is essentially low-spin.27... 

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]. 

The ambient temperature solution NMR spectra of the tris(dithiocarbamate) complexes, including those of Al (see above), show the complexes to be fluxional on the NMR chemical shift time scale. The stereodynamics can be quite complex with several different processes possible, namely, (1) a metal-centered rearrangement of the ligand polyhedron, (2) reversible ligand dissociation, (3) restricted rotation about the single N—C bonds of (bulky) N substituents. 

The homoleptic tris(dithiocarbamate) complexes [M(S2CNR2)3] (M = As, Sb, or Bi) have been studied extensively (93, 212-245). The arsenic complexes are mononuclear with three short As—S bonds (As—S = 2.31-2.39 A) that are essentially cis each other, and three long As—S bonds (As—S = 2.77-2.94 A). Valence bond sum (VBS) calculations show that the valency of the As atom is, as expected, close to three (224). The geometry at arsenic in the [As(S2CNR2)3] is best described as a distorted octahedron with the stereochemically active lone pair directed along the pseudo threefold axis, capping the triangular face defined by the three weakly coordinated S atoms (Fig. 16) (222-224, 230). 

Figure 16. The ORTEP plot of the coordination sphere of As in the tris(dithiocarbamate) complexes [As(S2CNR2)3]. The stereochemical active lone-pair caps the triangular face made by the three weakly bound S atoms, which are indicated by the dashed lines.

Other common species with this mode of coordination are the binuclear group 9 (VIII) complexes [M2(S2CNR2)5]" ", formed upon oxidation of tris(-dithiocarbamate) complexes, [M(S2CNR2)3] (M = Co, Rh) (Eq. 45) (302-311). 

It is noteworthy, however, that a study by Ymen and Stahl (357) suggested that for iron tris(dithiocarbamate) complexes with only aliphatic hydrocarbon substituents, the most important influence in determining their spin state (and... 

Bond and co-workers (303, 540,541) also utilized (ESMS) to study Ugand-exchange reactions. For example, while cobalt(III) tris(dithiocarbamate) complexes are inert to substitution and exchange reactions, they do undergo ligand exchange at elevated temperatures and upon controlled-potential oxidation and reduction (Fig. 59) (541). 

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