ISSN:
1572-901X
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Summary During interaction of ethanol-triethyl orthoformate solutions of nicotinic or isonicotinic acidN-oxides (LH and L′H, respectively) with MCl2 (M = Mn, Co, Ni), only one true adduct, of the Ni(LH)3Cl2 · 2 H2O type was obtained. In all other cases, partial substitution of Cl− ions with the corresponding pyridinecarboxylateN-oxide anionic ligands (L or L′) occurred. As a result, mixed ligands (LH-L or L′H-L′) were precipitated, as follows: Mn(LH)2LCl, Co(LH)LCl, Mn(L′H)L′Cl · 4H2O, Co(L′H)L′Cl · H2O and Ni2(L′H)L′Cl3 · 6 H2O. The insolubility of the new complexes in all common solvents, combined with the pronounced tendency of the 3- and 4-pyridinecarboxylates and theirN-oxides to function as bidentate bridging ligands, favours bi- or polynuclear structures. Spectral data suggest that Ni(LH)3Cl2 · 2 H2O is hexacoordinate, and the rest of the new complexes pentacoordinate. Bi- or polynuclear structures, involving double -M-(L)2-M- or-M-(LH)2-M- and single -M-(L′)-M- or-M(L′)-M-(L′H)-M- bridges, were proposed on the basis of the overall evidence; additional features of the proposed structural types are: exclusively coordinated chloro ligands, in all cases; aqua ligands [Co(L′H)L′Cl · H2O]; lattice water [Ni(LH)2Cl2 · 2H2O]; both lattice and coordinated H2O [Mn(L′H)L′Cl · 4H2O, and Ni2(L′H)L′Cl3 · 6H2O]; and, with the exception of Ni2(L′H)L′Cl3 · 6 H2O, terminal, unidentate, N-O oxygen-bonded LH or L′H ligands.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00623976
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