Crystal structures of isomorphous cadmium(II) and lead(II) oxalate trihydrates

The isomorphous cadmium(II) oxalate trihydrate (I) and lead(II) oxalate trihydrate (II) crystals belong to space groupP¯1 withZ=2. The crystallographic parameters for compoundI are:a=6.006(1),b=6.663(1),c=8.497(1)Å,a=74.76(1),=74.39(1), =80.94(1)°, andR=0.028 for 2643 observed MoK reflections; forII:a=6.008(1),b=6.671(1),c=8.493(1)Å,a=74.70(1),=74.33(1), =80.98(1)°, andR=0.065 for 4536 reflections. In the crystal structure, the metal atom is surrounded by seven oxygen atoms (including two aqua ligands) in the form of a distorted pentagonal bipyramid. The coordination polyhedra are interconnected through bridging oxalate groups to form a thick layer matching the (020) plane. Adjacent layers are further linked by hydrogen bonds involving both ligand and lattice water molecules to generate a three-dimensional network.On leave from Central Laboratory, Nankai University, Tianjin, China.