Bioanorganische Modellkomplexe für Metalloproteine des Eisen(III) und Mangan(III): Synthese, Magnetismus und Kristallstrukturen von [L₂Fe₂(acac)₂(μ-O)](ClO₄)₂, [L'Mn(acac)(OC₂H₅)]BPh₄ und [L'Mn(acac)(OH₂)](ClO₄)₂ (L = 1,4,7-Triazacyclononan, L' = N,N',N"-Trimethyl-1,4,7-triazacyclononan)

Abstract

Abstract The reaction of Fe(acac) 3 (acac = acetylacetonate, 2,4-pentanedionate) with 1,4,7-triazacyclo- nonane (L) in acetone in the presence of water and NaClO 4 yields green crystals of [L 2 Fe 2 III (acac) 2 (μ-O)](ClO 4 ) 2 (1) a μ-oxo bridged dimer of Fe(III) the crystal structure of which has been determined. Hydrolysis of this material in an acetone/water mixture in the presence of NaBr yields the green tetramer [L 4 Fe 4 III (μ-O) 2 (μ-OH) 4 ]Br 4 · 4H 2 O. Both compounds are strongly intramolecularly antiferromagnetically coupled. In contrast, the analogous reaction of Mn(acac) 3 with L or N,N',N"-trimethyl-1,4,7-triazacyclononane (L') in ethanol or methanol yields yellow- green monomeric complexes of the type [LMn III (acac)(OR)] + or [L'Mn(acac)(OR)] + (R = CH 3 , C 2 H 5 ) which were isolated as tetraphenylborate or hexafluorophosphate salts. The crystal struc­ture of [L'Mn(acac)(OC 2 H 5 )]BPh 4 (2) has been determined. If to the above reaction mixture cone. HClO 4 was added, red [L'Mn(acac)(H 2 O)](CLO 4 ) 2 (3) precipitated. In alkaline aqueous solution [L'Mn(acac)(OH)] + prevails. The crystal structure of 3 has also been determined. The new monomeric manganese(III) complexes have temperature independent (100-300 K) mag­netic moments of 4.8 to 5.1 μ B in agreement with a high spin (d 4 ) electronic configuration.