Structure of tetrasodium 1,4,5,8-naphthalenetetracarboxylate octahydrate

Na4[C14H4O8].8H2O, Mr = 536.3, monoclinic, P2(1)/n, a = 6.142 (1), b = 8.144 (3), c = 20.527 (4) A, beta = 93.97 (1) degrees, V = 1024.4 (5) A3, Z = 2, Dx = 1.74 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 2.14 cm-1, F(000) = 552 T = 295 K, R = 0.039 for 1769 unique reflections having I greater than sigma I. In this structure, the title compound has an inversion center at the midpoint of the central naphthalene ring bond. The average C-C bond length in the naphthalene core is 1.41 (3) A; the average interior angle is 119.9 (1.0) degrees. The exterior angle at the central naphthalene carbon is 122.7 (3) degrees, significantly smaller than in 1.8-substituted naphthalenes. The two inequivalent carboxyl groups adopt a non-planar arrangement with respect to the naphthalene core, making an average dihedral angle of 53.8 (1) degree with it. The two inequivalent sodium ions have quite different environments. Na(1) is coordinated by six O atoms in a highly distorted octahedral arrangement with an average Na-O distance of 2.44 (10) A. Na(2) is coordinated by five O atoms in a highly distorted trigonal bipyramidal arrangement with an average Na-O distance of 2.36 (3) A. Each of the eight inequivalent water H atoms is involved in a single hydrogen bond. The average H...O (acceptor) distance is 2.00 (5) A, the average O...O (acceptor) distance is 2.85 (5) A and the average O-H...O (acceptor) angle is 165 (8) degrees for these hydrogen bonds.(ABSTRACT TRUNCATED AT 250 WORDS)