STRUCTURES OF PARTIALLY DEUTERATED SODIUM TRIHYDROGEN DIMALONATE AND SODIUM HYDROGEN MALONATE (A REINVESTIGATION) AT 120-K

(1) Na+.C3(H,D)H2O4-.C3(H,D)2H2O4, M(r) = 230.11 (undeuterated), orthorhombic, Pnma, a = 8.484 (2), b = 6.859 (2), c = 14.950 (5) angstrom, V = 870.0 (7 angstrom3, Z = 4, D(x) = 1.757 g cm3, lambda(Mo K-alphaBAR) 0.71073 angstrom, mu = 1.951 cm-1, F(000) = 472, T = 120 K, R = 0.031 for 1064 observed reflections. (2) Na+.C3H3O4-, M(r) = 126.04, monoclinic, P2(1)/c, a = 6.671 (2), b = 7.390 (3), c = 9.359 (4) angstrom, beta = 100.49 (3)-degrees, V = 453.7 (5) angstrom3, Z = 4, D(x) = 1.845 g cm-3, lambda(Mo K-alphaBAR) = 0.71073 angstrom, mu = 2.363 cm-1, (000) = 256, T = 120 K, R = 0.025 for 1439 observed reflections. Partially deuterated sodium trihydrogen dimalonate is a superacid salt containing one malonic acid molecule and one hydrogen malonate ion. Three different asymmetric hydrogen bonds occur in this compound. The malonic acid molecule contains a short intramolecular hydrogen bond of length 2.532 (2) angstrom. One short [2.548 (2) angstrom] and one long [2.738 (2) angstrom] intermolecular hydrogen bond connect the malonic acid molecule and the hydrogen malonate ion forming infinite chains in the structure. A comparison is made with the crystal structure of sodium hydrogen malonate where the hydrogen malonate ions are connected by short asymmetric hydrogen bonds of length 2.5546 (9) angstrom forming infinite chains in the structure. In both compounds the Na ions are octahedrally coordinated by O atoms.