Actinide complexes nitrogen 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). 

Guillaumont, D. 2004. Quantum chemistry study of actinide(III) and lanthanide(III) complexes with tridentate nitrogen ligands. Journal of Physical Chemistry 108(33) 6893-6900. 

Ligand replacements for which kinetic data have been reported include [Ni(dgen)] + plus edta (parallel dissociative and associative paths), [Pb(edta)] plus R-( —)-pdta, polyether complexes of lead(n) plus nitrogen macrocycles, metal(ii)-oxine complexes plus edta, and a variety of analogous reactions involving lanthanide and actinide complexes (see Chapter 10). Kinetic data are also available for ligand exchange between trien and tetren complexes of cad-mium(ii) and the edta complex of copper(ii). ... 

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 silyl amide type ligands have been used extensively in rare earth chemistry, as well as in actinide and transition metal chemistry, to stabilize electronically unsaturated metal centers due to the available lone pair on the nitrogen donor atom. Because of the relatively larger steric encumbrance, the rare earth complexes with silyl amide type ligands often exhibit low coordination numbers. As a consequence, the large and electropositive rare earth metal centers are accessible to external reagents, which make them more active in many reactions. 

Actinide halides and oxyhalides are known to form numerous complexes with oxygen and nitrogen donor ligands and the preparation and properties of such compounds have recently been reviewed (12, 13). Relatively few protactinium halide complexes are known, but this situation reflects the lack of research rather than a tendency not to form complexes. However, there is sufficient information available for certain ligands to permit a comparison with the behavior of other actinide halides, and to illustrate the similarities and differences observed with the tetrahalides of thorium to plutonium inclusive and, to a lesser extent, with the protactinium and uranium pentahalides. 

Even fewer complexes with nitrogen donor ligands have been reported and all are methyl cyanide adducts (Tables X and XI). Protactinium pentabromide forms a soluble 1 3 complex in contrast to the 1 1 complexes formed by niobium and tantalum pentahalides (46). Other actinide pentahalide-methyl cyanide complexes are still unknown. Protactinium tetrachloride, tetrabromide, and tetraiodide react with anhydrous, oxygen-free methyl cyanide to form slightly soluble 1 4 complexes (44, 48) which are isostructural with their actinide tetrahalide analogs. 

Aside from the zinc complex, the coordination chemistry of the porphocyanines remains largely unexplored. Nonetheless, the pseudohexagonal arrangement of the six potentially donating nitrogen atoms present in porphocyanine has led to speculation that such systems could serve as ligands for larger cations such as those of the lanthanide or actinide series (as illustrated by the hypothetical structure... 

Orthophenanthroline complexes. As azides exhibit greater chemical affinity for trivalent actinide ions, we tried to check this behavior with a bidentate ligand. We chose 1-10 ghenantro-line which has two nitrogen donors at 2.75 A from each... 

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