Bridging behaviour of the 2-thiobarbiturate anion in its complexes with LiI and NaI

The structures of the Li-I and Na-I salts of 2-thiobarbituric acid (2-sulfanylidene-1-3-diazinane-4,6-dione, H(2)TBA) have been studied. mu-Aqua-octaaquabis(mu-2-thiobarbiturato-kappa O-2:O')bis(2-thiobarbiturato-kappa O)tetralithium(I) dihydrate, [Li-4(C4H3N2O2S)(4)(H2O)(9)]center dot 2H(2)O, (I), crystallizes with four symmetry-independent four-coordinated Li-I cations and four independent HTBA(-) anions. The structure contains two structurally non-equivalent Li-I cations and two non-equivalent HTBA(-) anions (bridging and terminal). Eight of the coordinated water ligands are terminal and the ninth acts as a bridge between Li-I cations. Discrete [Li-4(HTBA)(4)(H2O)(9)]center dot 2H(2)O complexes form two-dimensional layers. Neighbouring layers are connected via hydrogen-bonding interactions, resulting in a three-dimensional network. Poly[mu(2)-aqua-tetraaqua(mu(4)-2-thiobarbiturato-kappa O-4:O:S:S)(mu(2)-thiobarbiturato-kappa O-2:S)disodium(I)], [Na-2(C4H3N2O2S)(2)(H2O)(5)](n), (II), crystallizes with six-coordinated Na-I cations. The octahedra are pairwise connected through edge-sharing by a water O atom and an O atom from the mu(4)-HTBA(-) ligand, and these pairs are further top-shared by the S atoms to form continuous chains along the a direction. Two independent HTBA(-) ligands integrate the chains to give a three-dimensional network.