Catecholates, actinide

As with the actinide catecholates, we are interested in determining the optimum structure of actinide hydroxamates for use in the design of an octadentate actinide sequestering agent. 

Catecholate. Am and Pu complexes of sulfonated and carboxylated catecholamide ligands (CAMS and CAMC), including potentially octadentate chelators have been studied for their potential utility in removing actinides from humans via chelation. The complex coordination is pH dependent, with a triscatecholate Pu complex forming above pH 12. The stoichiometry of the Am complex was not determined however, its optical absorbance characteristics were determined. ... 

A significant effort has been made to prepare ligands with high specific affinity and selectivity for actinides that could be used for mammalian chelation therapy or as a specific extractant. A biomimetic approach to such ligand design, based on naturally occurring hydroxamate and catecholate siderophores and hydroxypyridinoate moieties, has been the most vital. The actinide... 

Tiron complexes of Th and other actinides have been prepared, generally in aqueous solution The EXAFS data have been modeled to include binding of the sulfonate group to Th at low pFI. This preferred complexation of a sulfonate over a catecholate, even at low pH, is unexpected. Bidentate catechol ligation of thorium Th(tiron)x, (x > 2), has been proposed at very high excess Tiron. 

Unusual mono(pentamethylcyclopentadienyl)actinide complexes containing a 15-membered trianionic hexaoxo ligand built from catechol and catecholborate have been prepared and structurally characterized. As depicted in Scheme 36, the synthesis of these complexes has been achieved by reacting Cp 2AnMe2 (An = Th, U) with an excess of catecholborane that contains 5% dimethylsulfide (DMS) in benzene at room temperature for 24 h. The DMS ligand could be replaced by THF.95... 

Table 4. Formation constants for some actinide (IV) hydroxamates and catecholates...

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