Crystal Structure and Electronic Absorption Spectrum of Double Neptunium(V) Phthalate Co(NH3)6NpO2[(OOC)2C6H4]2·2H2O

Single crystals of Co(NH3)6NpO2[(OOC)2C6H4]2·2H2O were grown. The crystal structure of this compound [monoclinic cell: a = 7.748(2), b = 23.051(5), c = 14.608(3) Å, β = 96.21(3)°, space group P21/c, Z = 4, V = 2593.7(9) Å3, dcalc = 2.034 g cm-3, CAD4 automatic diffractometer, MoKα, graphite monochromator, R1 = 0.041 for all 3567 reflections observed, wR2 = 0.1344 for all 4445 unique reflections, 325 refined parameters] was studied. The structure consists of infinite anionic chains {NpO2[(OOC)2C6H4]2}n3n-, [Co(NH3)6]3+ cations, and molecules of crystallization water. Neptunium(V) atom is in pentagonal-bipyramidal oxygen surrounding (CN 7); the neptunyl(V) group is linear and symmetrical; the Np = O bond lengths are 1.830(6) and 1.833(5)Å, the O = Np = O angle is 176.4(2)°. The equatorial plane of the bipyramid is formed by five oxygen atoms of phthalate anions. The Np-Oeq bond length correlates with the denticity of the phthalate anions. Two types of phthalate anions are localized in the structure. The first tridentate ligand is a bridge between Np(V) atoms in the chains. The second ligand is coordinated to Np in the bidentate fashion to form NpOCCCCO seven-membered chelate ring. The cation [Co(NH3)6]3+ has an octahedral structure. The average Co-N distance in the octahedron is 1.961 Å the N-Co-N bond angles are close to 90°. Two water molecules along with [Co(NH3)6]3+ cations are located between the anionic chains {NpO2[(OOC)2C6H4]2}n3n-. The chains are additionally bonded along the Z-axis of the crystal by Ow-H···O hydrogen bonds.