ISONICOTINATE N-OXIDE COMPLEXES WITH DIPOSITIVE 3D METAL-IONS

Divalent 3d metal complexes with isonicotinate N-oxide (N-inicO), of the type M(N-inicO)2·xH2O (M = Mn·Zn; x = 6 for M = Fe, Co, Ni, Zn; x = 5 for M = Mn; x = 2 for M = Cu), were prepared by reaction of (N-inicO)NH4 with the corresponding metal(II) acetates or ferrous ammonium sulfate in water. Desiccation of the preceding complexes over P4O10, under a vacuum of 10-4 torr, led to partial dehydration, affording the following lower hydrates: x = 5for M =Ni; x = 1.5 for M = Co, Zn;x = 1 for M = Cu; x = 0.5 for M = Mn, Fe. Characterization of the new metal complexes, based on spectral and magnetic studies, and the insolubility of all the complexes in water and organic solvents, led to their formulation as polynuclear of the following types: Hexa- and penta-hydrates; hexa-coordinated, [M(N-inicO)2(OH2]n·mH2O (m = 4n for M = Fe, Co,Ni, Zn; m = 3n for M = Mn, Ni), with the N- incO ligands forming single bridges between adjacent metal ions and functioning as bidentate, coordinating through the NO and one of the carboxylate oxygens; part of the non-coordinated COO oxygens are hydrogen-bonded to water, which is present in the form of both aqua ligands and lattice H2O. The lower hydrates of the type [(N-inicO2M-(OH2)-M(N-inicO)2)]n· bridging acqua ligand per two metal ions, as well as bidentate bridging N-inicO, being pentacoordinated of the type [(N-inocO)2M-(OH2)-M(N-inico)2]n· mH2O (m = O for M = Mn, Fe; m = 2n for M= CO, Zn). The dihydrate Cu(II) complex appears to be square-planar of the type [Cu(N-inicO)2]n·2nH2O, with bidentate bridging N-inicO ligands and exclusively lattice and H-bonded water. The corresponding monohydrate ([Cu(N-inicO)2]n·nH2O) probably contains both tetra-and penta-coordinated Cu2+ ions, with some N-inicO ligands acting at bidentate and some as tridentate (coordinating through the NO and the two COO oxygens) bridging. N-inicO is a 1igand of about the same strength as picolinate- and nicotinate-N-oxides. © 1979.