Synthetic, electrochemical and structural aspects of ß-diketonato and carboxylate complexes of aluminium

[摘要] English: A series of ferrocene-containing tris-β-diketonato aluminium(III) complexes of the formAl(FcCOCHCOR)3 (R = CF3, CH3, C6H5, Fc with Fc = ferrocenyl) were synthesized andsubjected to structural and electrochemical investigations. 1H NMR-spectroscopydistinguished between the mer and fac isomers of (FcCOCHCOPh)3 andAl(FcCOCHCOCH3)3. Al(FcCOCHCOCF3)3 existed only as the mer-isomer. A singlecrystal X-ray crystallographic determination of the structure of Al(FcCOCHCOCF3)3confirmed the existence of the mer-isomer (Z = 4, space group P212121). All Fc/Fc+electrochemical couples of Al(FcCOCHCOR)3 could be resolved cyclic voltammetrically.For R = Fc, formal reduction potentials of the ferrocenyl group were found to be Eo�? 33,123, 304, 432, 583 and 741 mV versus free ferrocene respectively. A cytotoxic studyshowed that aluminium(III) has an inhibiting effect on the cytotoxicity of ferrocenecontainingβ-diketones.Aluminium formate and acetate were synthesized from γ-Al2O3 as aluminium source and thecarboxylate bonding modes identified by FTIR. Dodecanoato and octadecanoato alumoxaneas well as aluminium dodecanoate, pentadecanoate, octadecanoate and ferrocenoate weresynthesized from the corresponding potassium carboxylate salts and aluminium trisisopropoxide.All complexes were characterized by FTIR and elemental analysis. It wasdifficult but not impossible to synthesize polymeric aluminium carboxylates with a 1:3 ratioof aluminium:carboxylic acid. It was found that the mode of carboxylate coordination toaluminium may be predicted by FTIR analyses. The difference in C=O stretchingfrequencies, Δν = νantisymmetric - νsymmetric > 200 cm-1indicate monodentate coordination. If 80< Δν < 120 the bonding mode is bridging, while 60 < Δν < 70 indicate bidentatecoordination. Asymmetric bidentate or monodentate coordination modes occur when 160 <Δν < 190 cm-1.

[发布机构] University of the Free State