Crystal Structure of Neptunium(V) Phthalate (NpO2)2(OOC)2C6H4·4H2O

Abstract

The crystal structure of (NpO2)2(OOC)2C6H4·4H2O [rhombic cell: a = 15.937(3), b = 26.922(5), c = 8.020(2) A, space group Pbcn, Z = 8, V = 3441.0(12) A3, d calc = 2.988 g cm- 3, CAD4, MoK α, graphite monochromator, 2934 independent reflections; R 1 = 0.0352, wR 2 = 0.0951] was studied. The structure consists of NpO2 + cations, H4C6(COO)2 2 - anions, and molecules of coordinated and crystallization water. The crystal lattice involves neutral layers [(NpO2)2(OOC)2C6H4(H2O)3] n parallel to the {101} plane. The dioxocations in these layers are bonded to each other to form cationic networks [the Np···Np distance is 3.911(1)-4.202(1) A]. The coordination polyhedra of Np(1) and Np(2) are pentagonal bipyramids (CN 7). The point group of the neptunyl(V) groups is close to D ∞h. These groups are bidentate ligands in the cation-cation interaction. The Np = O bond lengths are 1.852(6) [Np(1)-O(1)], 1.849(7) [Np(1)-O(2)], 1.845(7) [Np(2)-O(3)], and 1.841(7) A [Np(2)-O(4)]; the O = Np = O bond angles are 178.6(3)° [O(2)-Np(1)-O(1)] and 177.4(3)° [O(3)-Np(2)-O(4)]. The equatorial plane of the Np(1) bipyramid consists of two oxygen atoms of adjacent Np(2)O2 + dioxocations, two water molecules, and a single oxygen atom of the phthalate anion. The equatorial plane of the Np(2) bipyramid consists of two oxygen atoms of adjacent Np(1)O2 + dioxocations, two oxygen atom of the phthalate anion, and a single water molecule. The bond lengths in the equatorial plane of the bipyramid lie in the following ranges: Np-Oyl 2.373(7)-2.437(7) A (average 2.397 A) , Np-Ophth 2.360(7)-2.474(7) A (average 2.431 A), and Np-Owater 2.534(8)-2.558(9) A (average 2.544 A). The phthalate anions are tridentate bridging ligands binding neptunium atoms only within a single cationic network.