Preparation of rhodium(III)-2-ethylhexanoate

Rhodium (III) 2-ethylhexanoate, obtained by a method comprising the steps

• a) preparing an aqueous solution of an alkali salt of 2-ethylhexanoate by adding 2-ethylhexanoic acid to an aqueous alkali hydroxide solution at room temperature in a first reaction vessel, wherein the molar ratio of 2-ethylhexanoic acid to alkali hydroxide is 1.0:1.0 to 1.1:1.0 (mol/mol);
• b) providing a rhodium (III) precursor selected from rhodium (III) chloride hydrate, rhodium (III) chloride aqueous solution, and rhodium (III) nitrate aqueous solution, as well as mixtures thereof, in a second reaction vessel;
• c) mixing the aqueous solution of the alkali salt of 2-ethylhexanoate and the aqueous solution of the rhodium (III) precursor at an internal temperature of the reaction vessel of 20-30° C. to obtain a mixture;
• d) heating of the mixture from step c)
• to an internal temperature of the reaction vessel of 80-90° C., if the Rh(III) precursor is Rh(III) chloride aqueous solution or Rh(III) chloride hydrate, or
• to an internal temperature of 80-100° C. if the Rh(III) precursor is Rh(III) nitrate aqueous solution,
• to obtain a suspension;
• e) cooling of the suspension from step d) while stirring
• to an internal temperature of 40-50° C., if the Rh(III) precursor is Rh(III) chloride aqueous solution or Rh(III) chloride hydrate, or
• to an internal temperature of 55-65° C., if the Rh(III) precursor is Rh(III) nitrate aqueous solution,
• f) adding an alcohol that is immiscible with water, a carboxylic acid that is immiscible with water, or a mixture thereof, while stirring,
• g) stirring for 30 minutes to 3 hours,
• h) cooling to room temperature and leaving the resulting emulsion to settle,
• i) draining off the bottom, aqueous phase, and
• washing the top, product-containing organic phase with aqueous mineral acid, if the Rh(III) precursor in the step contains rhodium (III) chloride hydrate and/or rhodium (III) chloride aqueous solution, wherein the rhodium (III) 2-ethylhexanoate is free of rhodium (II) ethylhexanoate, which means that the UV/VIS spectroscopic measurement of a solution with a rhodium content of 1.9-2.1 wt % in 2 mm QS cuvettes at 597 nm exhibits an absorption band of an intensity less than of equal to 0.350.