Coordination of Macrocyclic Ligands to the Uranyl Ion

摘要

The uranyl ion, UO_2~(2+), is one of the most common fragments in actinide chemistry. It features an exclusively trans arrangement of its two oxo ligands. Indeed, there are no known examples of an authentic m-uranyl complex in the literature.1 Nonetheless, there is considerable interest in the synthesis of an authentic cis-uranyl complex, as this fragment should provide unique insights into actinide covalency and f-orbital participation in bonding. Previously, Clark and coworkers attempted to enforce cis-oxo stereochemistry by ligating a tripodal ligand to the uranyl framework.2 However, this resulted in ligand decomposition rather than the intended translcis isomerization. Drawing inspiration from the results of Clark and co-workers, we have begun to explore the ligation of 14-membered macrocyclic ligands to the uranyl fragment. We hypothesized that these macrocycles would be unable to accommodate the trans-UO_2~(2+) fragment within their small ring cavities, thereby forcing the desired trans to cis isomerization.