The syntheses of five new tetradentate ligands of bis(1,3-diketonate) type are described. The two diketonate moieties are connected by various long-chain spacers which allow the folding of the ligands for the formation of bis(1,3-diketonato)iron(III) complexes. These complexes exhibit, in the presence of imidazole, a catalytic activity towards the decomposition of hydrogen peroxide (catalase activity).Cet article decrit la synthese de cinq nouveaux ligands tetradentes 1,3-dicetoniques. Deux entites pentane-2,4-dione sont reliees entre elles par des espaceurs de longueurs differentes qui autorisent le repliement des ligands et la formation de complexes de fer(III). L'activite catalytique de decomposition du peroxyde d'hydrogene par ces complexes est etudiee.