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From the parent compound [Ca[Co(ethylenediamine)(oxalato) 2 ] 2 ] n •4H 2 O, 1, a series of framework compounds was prepared via the soluble sodium salt and crystal growth with the divalent metal ions Cd 2+ , Mn 2+ , and Sr 2+ , (2-4). These compounds have the same general formula [M[Co(ethylenediamine)(oxalato) 2 ] 2 ] n •xH 2 O and they all form the same four-and eight-connected 3D net having scu topology (and are thus isoreticular) with water filled channels of variable size running in one direction of the crystals. However, they crystallize in two different space groups, the chiral P2 1 (3, 4 and the low temperature form of 1) and the non-centrosymmetric P (1, 2). The potential voids upon water removal are 18-20% of the unit cell. Preliminary gas sorption measurements at 298 K and 8 bar

The utility of R 2 2 (9) biimidazole-carboxylate, R 2 2 (10) biimidazole-oxalate/squarate and R 2 2 (9) biimidazole-(tris-oxalate) synthons is considered for crystal engineering of hydrogen-bonded networks based on [Co III (H 2 biim) 3 ] 3+ cations (H 2 biim ) 2,2biimidazole) and oxalate, squarate or [M III (C 2 O 4 ) 3 ] 3anions. Syntheses and crystal structures are described for [3, and [Co III (H 2 biim) 3 ](C 2 O 4 )Cl • 5.5H 2 O, 4. Compounds 1 and 2 are isostructural and comprise [Co(H 2 biim) 3 ] 3+ cations bridged by [M(oxalate) 3 ] 3anions in two directions and water molecules in the third direction to give a 3D H-bonded network. Both outer and inner O atoms of the coordinated oxalate ions act as H-bond acceptors, forming motifs closely related to the anticipated R 2 2 (9) biimidazole-(tris-oxalate) synthon. Compound 3 contains a more complex H-bond pattern in 3D, built from the intended R 2 2 (10) biimidazole-squarate synthon and additional H-bonds between protonated squarate molecules and water molecules. The structure of compound 4 (obtained with synchrotron radiation) contains layers in which stacked pairs of oxalate anions bridge between [Co III (H 2 biim) 3 ] 3+ cations to form a dense 2D kgd-net, separated by layers of disordered chloride anions and H-bonded water molecules.