The crystal and molecular structure of uranyl diperchlorate heptahydrate, U02[CIOI]2*7H20, has been determined by single-crystal X-ray methods. The crystals are orthorhombic, space group Pca2,. with unit-cell dimensions a = 9.302(4), b = 14.692(6), and c = 10.842(5) B,Z = 4. 493 Reflections have been measured by a diffractometer and the structure solved by heavy-atom methods to R 0.046. The crystal contains [U02(OH2)s]2+, 2[CI04]-, and 2H20 in each asymmetric unit, held together by hydrogen bonds. The uranium has pentagonal-bipyramidal coordination with U-O(urany1) of 1.71 A (average), U-O(aqua) of 2.45 A (average), and 0 * * * 0 contacts of 2.88 A.ALTHOUGH the structures of a number of uranyl complexes have been determined in recent years,l very few have identical unidentate ligands. In. particular, the structure of the simple hydrated uranyl ion is unknown. This can only be examined in salts with anions of low coordinating power as, for example, [NO,]is co-ordinated to [UOJ2+ in preference to water, in aqueous solution and in the crystaL2 The perchlorate salt is suitable, and the structure of hydrated U02[C10,]2 (1) is reported here.

Secondary Bonding. Part 5.l The Crystal and Molecular Structures of Phenyliodine( 111) Diacetate and Bis(dich1oroacetate)

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