Preparation and properties of basic iron(III) carboxylates: Reactions of FeCl3 with some carboxylic acids

Anhydrous iron(III) chloride reacts with pure carboxylic acids RCOOH [where R = C2H5, n-C3H7, CH2Cl, CHCl2 and CCl3] at low temperature to yield Fe2Cl5 (OOCR)·nRCOOH [n = 3 when R = C2H5 and n-C3H7 and n = 2 when R = CH2Cl, CHCl2 and CCl3] and [Fe3O(OOCR)6(H2O)3][FeCl4] at about 70–80°C. These reactions reveal that no hydrogen chloride is evolved but an acyl chloride is formed. Pyridine combines with [Fe3O(OOCR)6(H2O)3][FeCl 4] (R = C2H5 and n-C3H7) to form [Fe3O(OOCR)6(C5H5N)3][FeCl4]. Piperidine, on the other hand, reacts with the elimination of piperidinium chloride to form [Fe3O(OOCR)6(H2O)3][Fe(NC5H10)4] compounds containing covalently bonded piperidide. Compounds containing polyatomic ligands such as NO3− and NCS− instead of the chloro group in [Fe3O(OOCR)6(H2O)3][FeCl4] (R = C2H5 and n-C3H7) have been prepared. All these compounds have been characterized on the basis of IR, UV-vis., molar conductance, molecular weight and room temperature magnetic susceptibility measurements.