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AIC5037 11Divalent 3d metal complexes with nicotinate N-oxide (N-nicO), of the type M(N-nicO)rxHzO (M = Mn-Zn; x = 4 or 5 ) , were synthesized by reaction of the corresponding metal(I1) acetates or ferrous ammonium sulfate with ammonium nicotinate N-oxide. The characterization of the new metal complexes was based on spectral, magnetic, and x-ray powder diffraction studies and their solubility characteristics. These compounds appear to be hexacoordinated, linear, polynuclear complexes of the type [M(N-nic0)2(0H2)2],.mH20 (m = 2n for M = Mn, Fe, Co, Ni, Cu; m = 3n for M = Zn), probably involving double M(N-nicO)zM bridges. The N-nicO ligands coordinate through the N-0 oxygen and one of the COO oxygens, while the other carboxylate oxygen is hydrogen bonded to water. Lattice water is also present in these complexes.Desiccation of the preceding compounds over PzOs, under reduced pressure, leads to their partial or complete dehydration.Under these conditions, only lattice water is eliminated from the Mn(II), Ni(II), and Cu(I1) complexes, without occurrence of any structural change. The Fe(I1) and Co(I1) complexes are completely dehydrated, while the Zn(I1) complex loses the lattice water and one aquo ligand per Zn2+ ion. Co(N-nic0)z seems to maintain coordination number 6, by the function of N-nicO as a tridentate bridging ligand, in a highly cross-linked polymeric structure. Fe(N-nic0)2 and Zn(N-nicO)yHzO appear to be pentacoordinated, comprising chemically nonequivalent carboxylate groups; evidence favors the presence of both bi-and tridentate N-nicO bridging ligands in the Fe(I1) complex and hydrogen-bonding of the uncomplexed COO oxygen of part of the bidentate ligands in the Zn(I1) complex. N-nicO is a ligand of strength about equal to that of picolinate N-oxide.

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Die hygroskopischen Titelkomplexe (I) werden durch Umsetzung entsprechender Metallperchlorate mit dem Phosphinoxid in Triethylorthoformiat dargestellt (Ausb.‐ Angaben fehlen).

Summary2,2,6,6-Tetramcthylpiperidine nitroxide free radical (TMPNO) complexes with ya* and Ln 3÷ (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er or Yb) perchlorates were synthesized and characterized by means of i.r. and e.s.r, spectral, magnetic susceptibility and molar conductance studies. The new complexes are of the general type [M(TMPNO')2(OH2)s(OCIO3)](CIOa) 2 (M = Y or Ln), involving two TMPNO, three aqua and one unidentate perchlorato ligand in the complex cation, and two anionic ClO4 groups. The NO bond-order in coordinated TMPNO is apparently two, as suggested by the i.r. evidence. The magnetic susceptibility and e.s.r, data were interpreted in terms of partial spin-spin coupling interaction between the unpaired electrons of the two TMPNO ligands, as well as unpaired f electrons, in the case of paramagnetic lanthanide(lll) ions. Severe steric hindrance, introduced during coordination of the free radical ligand through the NO oxygen atom, does not seem to allow accommodation of more than two TMPNO molecules in the inner coordination sphere of the central y3* or Ln 3÷ ion.

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