Product evolution in the Np(IV) fluorophosphate system

摘要

The reaction of (NpO2)-Np-237 with Cs2CO3, Ga2O3, H3PO4, and HF under mild hydrothermal conditions leads to the formation of NpFPO4 after 4 days at 180 degrees C. Heating at 180 degrees C for an additional 6 days leads to the crystallization Of Cs2Np2F7RO4 and NpF4. The Ga2O3 forms a GaPO4 matrix in which crystals of NpFPO4, Cs2Np2F7PO4, and NpF4 grow. Single crystal X-ray data reveal that the structure of NpFPO4 consists of Np(IV) centers bound by both fluoride and phosphate to yield [NpF2O6] distorted dodecahedra. these are linked by corner-sharing with fluoride and both corner- and edge-sharing with phosphate to yield a dense, three-dimensional network. The structure of Cs2Np2F7PO4 is Complex and contains both distorted dodecahedral [NpO2F6] and tricapped trigonal prismatic [NpO2F7] environments around Np(IV) that are linked with each other through corner- and edge-sharing, and with the phosphate groups to create a three-dimensional structure. There are small channels extending down the a-axis in Cs2Np2F7PO4. Crystallographic data: NpFPO4, orthorhombic, space group Pnma, a = 8.598(2), b = 6.964(1), c = 6.337(1) angstrom, Z = 4, V = 379.44(13) angstrom(3), R(F) = 3.53% for 40 parameters and 465 reflections with I > 2 sigma(I) (T = 193 K); Cs2Np2F7PO4, monoclinic, space group P2(1)/c, a = 8.8727(4), b = 16.2778(7), c = 7.8009(4) angstrom, beta = 112.656(1), Z = 4, V = 1039.73(8) angstrom(3), R(F) = 2.27% for 146 parameters and 2465 reflections with I > 2 sigma(I) (T = 193 K). (c) 2006 Elsevier Inc. All rights reserved.