METAL-BETAINE INTERACTIONS .21. CRYSTAL-STRUCTURES OF LITHIUM 3-CARBOXY-1-PYRIDINIOACETATE MONOHYDRATE AND SODIUM 3-CARBOXY-1-PYRIDINIOACETATE TETRAHYDRATE

Two hydrated alkali-metal salts of the betaine derivative 3-carboxy-1-pyridinioacetate, C5H4 (COOH)N+CH2COO-, have been prepared and investigated by X-ray crystallography. Lithium 3-carboxy-1-pyridinioacetate monohydrate (R(F) = 0.041 for 1144 observed MoKalpha data) has a one-dimensional polymeric structure based on a centrosymmetric Li2(acetato-mu-O,O')2 dimeric unit with the Li ion coordinated additionally by an intra-dimer acetate oxygen atom and an aqua ligand molecule in a slightly distorted tetrahedral LiO4 geometry [Li-O = 1.908 (4)-1.976(4)angstrom]. Sodium 3-carboxy-1-pyridinioacetate tetrahydrate (R(F) = 0.054 for 1812 observed data) features parallel columns of edge-sharing NaO6 Octahedra linked into a layer by bridging aqua ligands and betaine ligands whose acetato and carboxylato groups function in the unidentate and mu-O modes, respectively, with Na-O distances ranging from 2.351(2) to 2.608(2)angstrom. All the water molecules and uncoordinated carboxy oxygen atoms are involved in hydrogen bonding in both crystal structures.