CN109232227B - Synthesis method of rhodium trifluoroacetate dimer - Google Patents

Abstract

The invention discloses a method for synthesizing rhodium trifluoroacetate dimer, which comprises the following steps: taking hydrated rhodium chloride as a raw material, firstly synthesizing rhodium hydroxide, suspending in trifluoroacetic acid containing a reducing agent, heating and refluxing, concentrating under reduced pressure until the solid is nearly dry after being dissolved, then adding into the trifluoroacetic acid containing trifluoroacetic anhydride, evaporating under reduced pressure until the solid is nearly dry, and drying the solid in vacuum to obtain a rhodium trifluoroacetate dimer. The method avoids the synthetic route of ligand exchange taking rhodium acetate as a raw material, does not bring rhodium acetate impurities, has thorough raw material conversion, high product yield and good purity; trifluoroacetic acid recovered by reduced pressure distillation can be recycled as a reactant, so that the utilization rate of raw materials is improved, and the pollution to the environment is reduced; the process is simple to operate and is suitable for large-scale industrial production.

Description

Synthesis method of rhodium trifluoroacetate dimer

Technical Field

The invention belongs to the field of organic metal catalyst synthesis, and particularly relates to a method for synthesizing rhodium trifluoroacetate dimer.

Background

The rhodium trifluoroacetate dimer is similar to a rhodium perfluorobutyrate dimer (CAS number is 73755-28-9), is the most electron-deficient compound in the rhodium carboxylate dimer, is easy to perform ligand exchange along an axial position to form a rhodium carbene body, is an important rhodium homogeneous catalyst, is increasingly applied to organic synthesis such as metal carbene conversion, Sommelet-Hauser rearrangement, cycloisomerization and isomerization of eneyne and intramolecular redox reaction, and has the characteristics of mild reaction conditions, good activity and high selectivity.

Regarding the synthesis of Rhodium Trifluoroacetate dimer, the Preparation of Rhodium Trifluoroacetate dimer by ligand exchange method is reported in the documents entitled "Preparation and Properties of aqueous Rhodium (I1) Acetate and Some additives theory" and "Reactions of Rhodium trifluoracetate with variance bases of formation of 4: Complexes with Pyridine and tert-Butyl isocyanate and Rhodium hydride Bond", which are prepared by dissolving Rhodium Acetate in a mixture of trifluoroacetic acid and trifluoroacetic anhydride under heating and refluxing, evaporating the solvent to dryness under reduced pressure, repeating the process once, and recrystallizing and purifying the resulting solid and drying. Although the step of synthesizing rhodium trifluoroacetate by taking rhodium acetate as a raw material is simple, the cost of the rhodium acetate as the raw material is high, and the ligand exchange reaction cannot be completely carried out, so that impurities of the rhodium acetate as the raw material are brought into a recrystallized product.

Disclosure of Invention

The invention aims to provide a method for synthesizing rhodium trifluoroacetate dimer, which comprises the following steps:

(1) rhodium trichloride hydrate (RhCl)₃·nH₂O) dissolving in deionized water, adjusting the pH value of the solution by using alkali liquor, aging, performing suction filtration to separate rhodium hydroxide precipitate, and washing the precipitate until no chloride ions exist;

(2) dispersing the rhodium hydroxide precipitate into trifluoroacetic acid, dripping a reducing agent, carrying out reflux reaction, and carrying out reduced pressure evaporation to be nearly dry to obtain a blue-green solid;

(3) and (3) adding a mixed solution of trifluoroacetic anhydride and trifluoroacetic acid into the solid obtained in the step (2), heating and refluxing, evaporating under reduced pressure until the mixture is nearly dry, and drying to obtain a rhodium trifluoroacetate dimer product.

In the method for synthesizing the rhodium trifluoroacetate dimer, the mass ratio of the rhodium trichloride hydrate to the deionized water in the step (1) is 1: 8-25.

In the method for synthesizing rhodium trifluoroacetate dimer, the alkali solution in step (1) may be one or two or more of a sodium hydroxide solution, a potassium hydroxide solution, a sodium carbonate solution and a sodium bicarbonate solution. Preferably, the mass concentration of the alkali liquor is 5-20%.

Wherein, in the synthesis method of the rhodium trifluoroacetate dimer, the conditions of adjusting the pH value of the solution by the alkali liquor in the step (1) are as follows: adjusting the pH to 8-10 (e.g., 8.5-9.5) at 50-70 deg.C (e.g., 55-65 deg.C).

In the method for synthesizing rhodium trifluoroacetate dimer, the aging time in the step (1) is 15-30 min, for example, aging for 20 min.

In the method for synthesizing rhodium trifluoroacetate dimer, the liquid-solid ratio (mL/g) of trifluoroacetic acid to rhodium hydroxide precipitate in step (2) is 10-100: 1, for example 20-70: 1.

In the method for synthesizing rhodium trifluoroacetate dimer, the reducing agent in step (2) is one or two or more of methanol, ethanol, formic acid and formaldehyde.

In the method for synthesizing the rhodium trifluoroacetate dimer, the molar ratio of the reducing agent to the rhodium trichloride hydrate in the step (2) is 0.5-15: 1, for example, 0.5-10: 1.

In the method for synthesizing the rhodium trifluoroacetate dimer, the temperature of the reflux reaction in the step (2) is 50-110 ℃ (for example, 70-90 ℃), and the reflux time is 0.5-4 h (for example, 1.5-2.5 h).

In the method for synthesizing rhodium trifluoroacetate dimer, the near-dry component in the step (2) may be solid and slurry, and the water content is 15-40%, for example.

In the method for synthesizing rhodium trifluoroacetate dimer, the mass-to-volume (g/mL) ratio of trifluoroacetic anhydride to trifluoroacetic acid in the mixed solution in the step (3) is 1: 5-20, for example, 1: 5-10.

Preferably, the volume-to-mass ratio (mL/g) of the mixed solution to the rhodium trichloride hydrate is 10-20: 1.

In the method for synthesizing the rhodium trifluoroacetate dimer, the heating reflux temperature in the step (3) is 50-90 ℃, and the reflux time is 0.5-2 h.

In the method for synthesizing rhodium trifluoroacetate dimer, the near-dry component in the step (3) may be solid and slurry, and the water content is 15-40%, for example.

Wherein, the synthesis method of the rhodium trifluoroacetate dimer has the drying temperature of 100-120 ℃ in the step (3).

In the method for synthesizing the rhodium trifluoroacetate dimer, the color of rhodium hydroxide in the step (1) is brown yellow, and the color of the product in the step (3) is green.

The invention has the beneficial effects that: the method avoids a synthesis route of ligand exchange by taking rhodium acetate as a raw material, does not bring rhodium acetate impurities, has thorough raw material conversion, high product yield (> 84.5%) and high purity (> 99%); trifluoroacetic acid recovered by reduced pressure distillation can be recycled as a reactant, so that the utilization rate of raw materials is improved, and the pollution to the environment is reduced; the process is simple to operate and is suitable for large-scale industrial production.

Detailed Description

The technical solution of the present invention will be further described in detail with reference to specific embodiments. The following examples are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of the invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

Unless otherwise indicated, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

Example 1

Dissolving 5.00g of rhodium trichloride hydrate in 100mL of deionized water, stirring and heating to 60 ℃, dropwise adding a sodium hydroxide solution with the mass fraction of 10% to adjust the pH value to 9, aging for 20min, performing suction filtration to separate rhodium hydroxide precipitate, washing the precipitate with deionized water until no chloride ion exists, stirring and dispersing the obtained precipitate in 200mL of glacial acetic acid, adding 1g of formic acid, performing reaction reflux at 80 ℃ for 2h, performing reduced pressure evaporation until the precipitate is nearly dry to separate out a blue-green crystal, adding 90mL of trifluoroacetic acid and 10mL of trifluoroacetic anhydride into the blue-green solid, performing heating reflux for 0.5h, performing reduced pressure evaporation until the precipitate is nearly dry, and drying at 110 ℃ to obtain 5.36g of green solid, wherein the product yield is 84.93%, and the purity is 99.0%.

Example 2

Dissolving 5.00g of rhodium trichloride hydrate in 100mL of deionized water, stirring and heating to 60 ℃, dropwise adding a sodium carbonate solution with the mass fraction of 10% to adjust the pH value to 9, aging for 20min, carrying out suction filtration to separate rhodium hydroxide precipitate, washing the precipitate with deionized water until no chloride ion exists, stirring and dispersing the obtained precipitate in 200mL of glacial acetic acid, adding 1.5g of 37% formaldehyde solution, carrying out reaction reflux for 1.5h at 70 ℃, carrying out reduced pressure evaporation until the precipitate is nearly dry to separate out blue-green crystals, adding 90mL of trifluoroacetic acid and 10mL of trifluoroacetic anhydride into the blue-green solids, carrying out heating reflux for 0.5h, carrying out reduced pressure evaporation until the precipitate is nearly dry, drying at 110 ℃ to obtain 5.39g of green solids, wherein the product yield is 85.11%, and the purity is 99.0%.

Example 3

Dissolving 5.00g of rhodium trichloride hydrate in 100mL of deionized water, stirring and heating to 60 ℃, dropwise adding a sodium carbonate solution with the mass fraction of 10% to adjust the pH value to 9, aging for 20min, carrying out suction filtration to separate rhodium hydroxide precipitate, washing the precipitate with deionized water until no chloride ion exists, stirring and dispersing the obtained precipitate in 200mL of glacial acetic acid, adding 1g of formic acid, carrying out reaction reflux at 80 ℃ for 2h, carrying out reduced pressure evaporation until the precipitate is nearly dry to separate out a blue-green crystal, adding 90mL of trifluoroacetic acid and 10mL of trifluoroacetic anhydride into the blue-green solid, carrying out heating reflux for 0.5h, carrying out reduced pressure evaporation until the precipitate is nearly dry, drying at 110 ℃ to obtain 5.47g of green solid, wherein the product yield is 86.45%, and the purity is 99.1%.

Example 4

Dissolving 20.00g of rhodium trichloride hydrate in 400mL of deionized water, stirring and heating to 60 ℃, dropwise adding a sodium carbonate solution with the mass fraction of 10% to adjust the pH value to 9, aging for 20min, performing suction filtration to separate rhodium hydroxide precipitate, washing the precipitate with deionized water until no chloride ion exists, stirring and dispersing the obtained precipitate in 600mL of glacial acetic acid, adding 4g of formic acid, performing reaction reflux at 80 ℃ for 2h, performing reduced pressure evaporation until the precipitate is nearly dry to separate out a blue-green crystal, adding 250mL of trifluoroacetic acid and 50mL of trifluoroacetic anhydride into the blue-green solid, performing heating reflux for 0.5h, performing reduced pressure evaporation until the precipitate is nearly dry, and drying at 110 ℃ to obtain 21.76g of green solid, wherein the product yield is 86.15% and the purity is 99.3%.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (1)

1. A synthetic method of rhodium trifluoroacetate dimer is characterized by comprising the following steps:

dissolving 5.00g of rhodium trichloride hydrate in 100mL of deionized water, stirring and heating to 60 ℃, dropwise adding a sodium hydroxide solution with the mass fraction of 10% to adjust the pH value to 9, aging for 20min, performing suction filtration to separate rhodium hydroxide precipitate, washing the precipitate with deionized water until no chloride ion exists, stirring and dispersing the obtained precipitate in 200mL of glacial acetic acid, adding 1g of formic acid, performing reaction reflux at 80 ℃ for 2h, performing reduced pressure evaporation until the precipitate is nearly dry to separate out a blue-green crystal, adding 90mL of trifluoroacetic acid and 10mL of trifluoroacetic anhydride into the blue-green solid, performing heating reflux for 0.5h, performing reduced pressure evaporation until the precipitate is nearly dry, and drying at 110 ℃ to obtain 5.36g of green solid, wherein the product yield is 84.93%, and the purity is 99.0%.