Synthesis and Single Crystal Investigation of Two-Dimensional Rectangular Network [M(4,4 ' -bpy) (Phth)(H2O)](n). 2H(2)O with Small Neutral Cavities Two isostructural neutral coordination polymers [M(4,4 ' -bpy)(phth)(H2O)]}(n)-2H(2)O, where M = Co2+, Cd2+, comprising rectangular grids with each cavity enclosed by two 4,4 ' -bipyridine (4,4 ' -bpy) and two phthalate (phth) ligands, which superpose in an offset fashion reducing the channel size to include two water molecules, have been synthesized and structurally characterized by single crystal X-ray diffraction.