Crystal and molecular structures of µ-oxalato-di[bisethylenediamine-nickel(II)] dinitrate, µ-oxalato-bis[di-(2-aminoethyl)aminecopper(II)] di-perchlorate, and µ-oxalato-bis[di-(3-aminopropyl)aminezinc(II)] diperchlorate
Crystal and molecular structures of the title compounds are reported. In each the complex cation is dimeric with the planar oxalate group acting as a bridge by forming five-membered chelate rings with two metal centres. Co-ordination geometries are approximately octahedral in the nickel compound (I), square pyramidal in the copper compound (II)(oxalate oxygen atoms occupying one basal and one axial site), and trigonal bipyramidal in the zinc compound (III)(oxalate oxygens occupying one apical and one equatorial site). The conformations of the co-ordinated amines are discussed and their relationships with the stereochemistry of the metal centres and with the hydrogen bonding network examined. Crystal data: (I), monoclinic a= 6·33(2), b= 12·03(2), c= 14·95(3)Å, β= 91·2(3)°, Z= 2, space group P21/n; (II), orthorhombic. a= 7·02(1), b= 13·25(3), c= 25·27(4)Å, Z= 4, space group Pbc2l; (III), orthorhombic, a= 13·38(2), b= 14·72(3), c= 13·30(3)Å, Z= 4, space group Pna2l. The structures were solved by the heavy-atom method from photographic data and refined by least squares to R 0·105 [(I), 1936 independent reflexions], 0·101 [(II), 1948], and 0·090 [(III), 1688].