COORDINATION POLYMERS OF MN(II) WITH THE LIGAND PYRAZINE-2,3,5,6-TETRACARBOXYLIC ACID

Two coordination polymers of Mn(II) with the ligand pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) have been prepared. The reaction of MnSO4 with H4PZtC (ratio 1:1) carried out at 50-degrees-C gave a zig-zag polymer structure with the ligand coordinated in a pseudo bis(tridentate) fashion (1) (crystal data: C8H10N2O12Mn, tetragonal, space group I4(1)/a, a=b=13.934(l), c=13.578(l) angstrom, Z=8, 1670 reflections with I>3sigma(I), R=0.029). The reaction of an excess of MnSO4 with H4PZtC (ratio 3:1) at room temperature gave the salt [Mn(H2O)6][H2pztc] (2) (crystal data: CH14N2O14Mn, Monoclinic, space group A2/n, a=6.83(1), b=9.918(l), c=22.051(2) angstrom, beta=102.91(2)-degrees, Z=4, 1547 reflections with 1>3sigma(I), R=0.026). The anion possesses a strong intramolecular H bond and is found coordinated to the Mn atom in polymer 1. The reaction of MnSO4 with H4PZtC (ratio 1:1) carried out at 50-degrees-C in the presence of the equimolar buffer CH3COOK/CH3COOH, gave a column type polymer with the ligand coordinated in a mono(tridentate)-bis(monodentate) fashion (3) (crystal data: C8H7N2O11.25K2Mn, monoclinic, space groupI2/a, a=18.207(2), b=8.335(l), c=19.185(3) angstrom, beta=103.66(1)-degrees, Z=8, 1539 reflections with I>2sigma(I), R=0.041). The reaction of H4PZtC with ZnC]2 (ratio 1:1) in the presence of the same equimolar buffer solution lead to the formation of the isomorphous polymer Zn-3 (crystal data: C8H7N2O11.25K2Zn, monoclinic, space group I2/a, a=18.194(l), b=8.264(l), c=18.924(l) angstrom, beta=103.92(l)-degrees, Z=8, 2567 reflections with I>3sigma(I), R=0.031).