A Planar [15]Metallacrown-5 That Selectively Binds the Uranyl Cation Note from the editor: According to IUPAC recommendations hydroxamic acid is retained as the name of a class, but the compounds are preferably named as N -hydroxy amides. The systematic name of the triply deprotonated ion salicylhydroximate (used throughout this communication) is thus N ,2-dioxi-dobenzoyl amide.