X-ray structure determination of two related uranyl phosphate crown ether compounds

Two new uranyl phosphate compounds have been prepared and their structures determined. [UO2(H2PO4)(2)(H2O)](2).(18-crown-6) . 5H(2)O (1) and UO2(H2PO4 )(2)(H2O).(18-crown-6). 3H(2)O (2) contain neutral one-dimensional [UO2(H2P O4)(2)(H2O)](infinity) chains that are nearly identical to those of a previ ously reported binary phosphate, UO2(H2PO4)(2)(H2O). 2H(2)O (3). The new co mpounds, however, crystallized with either one-half or one 18-crown-6 molec ule per uranium atom for 1 and 2, respectively. The seven-coordinate uraniu m(VI) assumes a pentagonal bipyramidal configuration, which is common for u ranyl compounds. Empty 18-crown-6 molecules are hydrogen bonded to the uran yl phosphate chains as well as to lattice water molecules and function as ' packing-directing' agents. (C) 2000 Elsevier Science Ltd. All rights reserv ed.