Synthesis and thermal transformation of a neodymium(III) complex [Nd(HTBA)2(C2H3O2)(H2O)2]·2H2O to non-centrosymmetric oxosulfate Nd2O2SO4
Neodymium complex [Nd(HTBA)2(C2H3O2)(H2O)2]n·2nH2O (1) (H2TBA = 2-thiobarbituric acid, C4H4N2O2S) has been synthesized in an aqueous solution at 80–90 °C. The crystal structure of 1 has been determined by the Rietveld method in space group P21/n, a = 8.5939(2), b = 22.9953(5), c = 10.1832(2) Å, β = 112.838(1)°, Z = 4, and R = 0.0181. In 1, the Nd(III) is coordinated by four μ2-HTBA– ions through O, three oxygens from two μ2-η2 : η1-bridging CH3COO– anions, and two terminal waters with a tri-capped trigonal prism structure. The prisms form an edge-contact pair through two O from two acetates. The pairs are connected by HTBA– and form a 3-D framework. The principle product of thermal decomposition of 1 at >750 °C is Nd2O2SO4 (2). The crystal structure of 2 has been obtained in space group I222, a = 4.1199(4), b = 4.2233(4), c = 13.3490(12) Å, Z = 2, and R = 0.0246. The structure is related to an orthorhombic structure type of M2O2SO4 (M = Ln) compounds. In 2, the Nd3+ is coordinated by six oxygens in a trigonal prism. Each NdO6 prism links with two SO4 tetrahedra by nodes, with four other NdO6 prisms by edges, and with four other NdO6 prisms by nodes, and the units form the 3-D frame. In the frame, the layers of SO4 tetrahedra are alternated by two NdO6 prism layers.
