Synthesis and crystal structure of a new Np(V) oxalate, Na 4(NpO2)2(C2O4) 3·6H2O

A new oxalate complex, Na4(NpO2)2(C 2O4)3·6H2O, with the Np : C2O4 ratio of 2:3 was synthesized and studied by single crystal X-ray diffraction. In the crystal, the NpO2+ cations and oxalate anions are bound in open networks [(NpO2) 2(C2O4)3]n4n- parallel to the bc plane. The Na(1) cations are accommodated in large voids of the neptunyl oxalate networks with the formation of crimped mixed-cation layers of the composition [Na2(NpO2)2(C 2O4)3]n2n-. The negative charge of the layers is compensated by the Na(2) cations arranged between the layers. The Np atoms have a pentagonal bipyramidal coordination surrounding with the equatorial plane formed by the oxygen atoms of three oxalate anions. The structure contains tridentate-bridging and tetradentate-bridging oxalate anions. © Pleiades Publishing, Inc., 2006.