CRYSTAL-STRUCTURES OF CS3NPO4(OH)2.3H2O AND RB3NPO4(OH)2.3H2O

The x-ray structure of Cs3NpO4(OH)2.3H2O (I) is solved (CAD4 SDP autom ated diffractometer, lambda Mo Kalpha, graphite monochromator). Crysta llographic data: space group C2/c, a = 12.590(3), b = 11.550(2), c = 8 .051(1) angstrom, beta = 91.60(2)-degrees, V = 1170 angstrom3, Z = 4, d(calc) = 4.47 g/cm3, R = 0. 050, R(w) = 0. 062 for 863 reflections an d 64 parameters. The structure of I can be described as closest packed anionic chains of {[NpO4(OH)2].3H2O}n3n- (anions [NpO4(OH)2]3- and wa ters of crystallization joined by H-bonds) and twice as many chains of Cs+. The centrosymmetric anions are almost ideal tetragonal bipyramid s with equatorial distances Np - 0 1. 90(1) and 1. 89 (1) angstrom and axial distances Np - O(OH) 2.41 (1) angstrom. The structure is compar ed with those of other Np(VII) compounds. A preliminary investigation of a Rb3NpO4(OH)2.3H2O single crystal (the composition is assigned ass uming it is isostructural with I) demonstrated that the Rb salt crysta llizes in the same space group with a = 12.23, b = 11.12, c = 7.82 ang strom, beta = 91.2-degrees, V = 1063 angstrom3, and d(calc) = 4.03 g/c m3.