COORDINATION-COMPLEXES OF IRON(III) WITH 3-HYDROXY-2(1H)-PYRIDINONE, 2,3-DIHYDROXYBENZOIC ACID AND 3,4-DIHYDROXYBENZOIC ACID - PREPARATION AND CHARACTERIZATION IN THE SOLID-STATE

The synthesis and study of a number of new iron(III) complexes of the ligands 3-hydroxy-2(1H)-pyridinone (3,2-opoH), 2,3-dihydroxybenzoic ac id (2,3-dhbH3) and 3,4-dihydroxybenzoic acid (3,4-dhbH3) are described . These complexes have the formulae [Fe(3,2-OPO)2Cl]-Pr(n)OH, K[Fe(2,3 -dhbH)2(H2O)2], [Fe(2,3-dhb)(H2O)2], K[Fe-(3,4-dhbH)2(H2O)2], [Fe(3,4- dhb)(H2O)2] and K6[Fe(3,4-dhb)3].3H2O. The complexes were characterize d by elemental analyses. X-ray powder patterns, t.g.a./d.t.g. techniqu es, magnetic susceptibilities and spectroscopic (u.v.-vis., i.r. and v ariable-temperature Fe-57-Mossbauer) studies. Monomeric octahedral str uctures are assigned for the 1:2 2,3-dhbH-2- CoMplex and the 1:3 3,4-d hb3-compound. Dinuclear and/or oligonuclear structures are tentatively proposed for the remaining complexes in the solid state. In [FeL(H2O) 2] (L3- = 2,3-dhb3- or 3,4-dhb3-), iron(III) appears to be 5-coordinat e. Both oxygens of 3,2-opo- participate in coordination, while the dih ydroxybenzoato ligands exhibit various coordination modes, depending m ainly on the positions of the hydroxy groups, their anionic charge and the ligand:metal molar ratio used.