Preparation and crystal structure of sodium tris(p-amino-salicylato) dioxouranium(VI) hydrate

Abstract

The synthesis and crystal structure of the title compound are described. The complex crystallizes in the trigonal system, space group P31c with a = 16.053(12), $\text{c = 6.839(8)}\text{A}\text{̊}$ and Z = 2. The structure was solved by the heavy-atom method from 1252 counter reflections, and refined by least-squares methods to R 0.054. Six carboxylate oxygen atoms belonging to the three nearly planar p-amino-salicylate ions fill the equatorial region of the linear uranyl ion, giving the U atom an hexagonal-bipyramidal coordination overall. The hexagon is slightly puckered (± 0.05 Å), bond lengths and angles are as expected [U-O(apical) 1.78(e), U-O(eq) 2.47(2) Å]. The exact water content (and thereafter the Na⁺ coordination) is not entirely certain, but seems to approximate to 6H₂O. The intramolecular hydrogen bond between the phenolic and a carboxylate oxygen atom, present in the free acid, is not destroyed by coordination.