Crystal Growth and Structure of NiC4H4O6·2.5H2O

Single crystals of nickel tartrate hemi-pentahydrate, NiC4H4O6·2.5H2O, were grown by the gel method using silica gels. The crystal structure was determined by the single-crystal X-ray diffraction method. Its structure was orthorhombic with space group P212121 and lattice constants a = 7.8578(3) Å, b = 11.0988(5) Å, and c = 18.0529(8) Å, and consisted of slightly distorted NiO6 octahedra, C4H4O6 and H2O molecules, C4H4O6–Ni–C4H4O6 chains containing H2O molecules, and O–H···O hydrogen-bonded frameworks between adjacent molecules. The C4H4O6 molecules contained both single and double C–O bonds, and single C–C bonds, similar to other tartrate compounds. We discussed the differences in the chemical formulae and structures of tartrate compounds induced by different cations of the first transition metal series.