SYNTHESIS AND CHARACTERIZATION OF SOME METAL(II) COMPLEXES OF QUINOLINIC ACID (H-2-QUIN) AND X-RAY CRYSTAL-STRUCTURES OF [NI(H-QUIN)2(H2O)2] AND [MN(H2O)6][MN(H-QUIN)3]2

Complexes of the types M(H-Quin)2 . 2H2O (M = Mn, Co, Ni and Zn) and M (H-2-Quin)(Quin) . 2H2O (M = Fe and Co), where H-2-Quin = quinolinic a cid, have been prepared and characterized. The spectral results sugges t that all these complexes contain distorted octahedral metal atoms. T he crystal structures of the nickel(II) and manganese(II) complexes we re determined by single-crystal X-ray diffraction methods. The nickel atom in centrosymmetric Ni(H-Quin)2 . 2H2O is octahedrally coordinated by two nitrogen atoms [Ni-N = 2.030(2) angstrom] and two oxygen atoms [Ni-O = 2.027(2) angstrom] belonging to the two H-Quin- anions and tw o trans-aqua molecules at Ni-O distances of 2.117(2) angstrom. The str ucture is consolidated by intra- and intermolecular O-H ... O hydrogen bonds. X-ray analysis of the Mn(H-Quin)2 .2H2O complex revealed that it should be formulated as [Mn(H2O)6][Mn(H-Quin)3]2. The octahedral [M n(H-Quin)3]- and [Mn(H2O)6]2+ units lie on different three-fold axes a nd are connected together by O-H ... O hydrogen bonds between the aqua ligands and the non-coordinated oxygen of a carboxylato group or oxyg en atoms of the carboxy group in position 3 in the pyridine ring.