Lithium hydrogen iodo­fumarate monohydrate

Yellow crystals of the title compound, poly[[aqua­lithium(I)]-μ₃-iodo­fumarato], [Li(HOOC—CH=CI—COO)(H₂O)]_n, crystallized unexpectedly from an aqueous solution containing acetyl­ene­dicarboxylic acid and LiI. The lithium cation is coordinated tetra­hedrally by four O atoms of three iodo­fumarate anions and one water mol­ecule. These tetra­hedra are connected such that a layered coordination polymer is formed.