Actinide complexes sulfur ligands

Actinide complexes with chelating ligands containing sulfur and amidic nitrogen donor atoms. U. Casellato, M. Vidali and P. A. Vigato, Coord. Chem. Rev., 1979, 28, 231-277 (181). 

Aside from the subtle effect of the An-amine binding in the An-DTPA complexes of TALSPEAK, and the chloride, thiosulfate interaction with the actinides in ion-exchange studies, we have not discussed the proposal that there is of slightly greater covalency in actinide complexation (both by hydrophobic and hydrophilic ligands). In this section, the effect of binding of actinides to nitrogen and sulfur donor molecules is discussed within this model. 

The actinide cations are hard acids, that is, their binding to ligands is described in terms of electrostatic interactions, and they prefer to interact with hard bases such as oxygen or fluorine rather than softer bases such as nitrogen or sulfur. The actinide cations do form complexes with the soft bases but only in nonaqueous solvents. 

The fact that dithiophosphinic acids show the greatest selectivity for An over Ln " as compared to phosphinic and monothiophosphic acids is due to an increased covalency in the An—S bonds but not necessarily a shorter An—S bond. In addition, trivalent actinides show a thermodynamic preference to form bonds with soft donor atoms. The structural differences observed in the complexes of An with the three ligands studied are due to differences in the hard and soft nature of the oxygen and sulfur atoms, respectively, and their hydrogen-bonding ability."" ... 

Sulfur donor ligands. Complexes of actinides or lanthanides ions with sulfur donor ligands such as dithiocarbamate (S2CNR2)... 

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