MXPA98008169A - Preparation of substituted aromatic amines - Google Patents

Abstract

A method for producing aromatic amines such as N-phenyl-p-phenylenediamine is disclosed wherein an amine substituted aromatic such as aniline is oxidized with oxygen or hydrogen peroxide in the presence of a preferred trisodium pentacyano ferrate(II) complex containing various water soluble ligands, such as ammonia, mono alkyl amine, dialkyl amines, and trialkyl amines. The complex is subsequently catalytically reduced by hydrogenation using certain heterogeneous metal catalysts to yield the desired aromatic amine.

Description

PREPARATION OF SUBSTITUTE AROMATIC AMINES BACKGROUND OF THE INVENTION 1. Field of Invention The present invention relates to the methods for the production of phenyl-p-phenylenediamine (FFDA) and higher amines of the structural formula (I) given below, starting with the initial material of structural formula (II) given further down. More particularly, it is related to a method for the preparation of FFDA in which the aniline is oxidized in the presence of trisodium pentacyanoferrate (II) complexes containing various water-soluble ligands, such as ammonia, monoalkylamine, dialkylamines and trialkylamines, and using oxygen or hydrogen peroxide as the oxidizing agent. The compound is then reduced by hydrogenation using suitable heterogeneous metal catalysts. where n is equal to 2 to 5, and Ri and R2 are defined below (II) Ri and R2 may be the same or different, they must be ortho or meta to the amino group, and may be hydrogen, C1-C4 alkyloxy C1-C4 alkoxy, halogen, cyano, carboxylate salts and carboxylic acid amides or mixtures of the same. The present invention is related to the production of FFDA with the ability to recirculate the transition metal complex, high selectivity and performance. The conversion of aniline to N-phenyl-p-phenylenediamine is within the limits of 40 to 85%. The performance of FFDA varies from 91% to 97%. The method of the present invention is also cost effective and does not produce undesirable byproducts for the environment. 2. Background of Related Art. The production of p-phenylenediamine and its derivatives is very widespread and the uses thereof are well known. In Patent No. , 17, 063 of the U., Stern and colab. disclose various methods of preparing N-phenyl-p-phenylenediamine in which aniline and nitrobenzene react under specific conditions. In other publications, the oxidative dimerization of aniline to produce N-phenyl-p-phenylenediamine is disclosed. British Patent No. 1, 400,767 and European Patent 0-261096 use an alkaline metal ferricyanide, while European Patent 0-272-238 uses a hypohalite oxidizing agent. None of these processes is very selective, nor do they produce good conversions. J. Bacon and R. N. Adams in J Am. Chem. Soc, 90 p. 6596 (1968) report the anodic oxidation of aniline to N-phenyl-p-quinonadiimine but do not give conversions or yields. E. Herrington, in J. Chem. Soc. P. 4683 (1958) reports the oxidative dimerization of aniline with pentacyanoaminoferrate (ll l) disodium to form a complex containing N-phenyl-p-phenylenediamine, which is then chemically reduced with reducing agents such as hydrazine hydrate, sodium dithionate, sodium hydrosulfite and hydrogen sulfide. The use of the trisodium pentacyanoferrate (II) complex and the catalytic reduction with hydrogen used in this invention distinguish it from this publication and the differences result in a significantly better process. The stoichiometry of the present invention is much better than that of Herrington since higher ratios of aniline to complex can be used in the process described herein. Therefore, an object of the present invention is to provide a method for the production of N-phenyl-p-phenylenediamine and related compounds. Another object of the present invention is to disclose a method for the production of such compounds by means of an aqueous process which allows the easy removal of unreacted aniline and the subsequent separation of the initial complex reconstituted from the desired end product [formula (i)). )] after the reduction, thus providing a process that is commercially viable, which involves both a low cost as well as the recirculation capacity.

It is also an object of the present invention to provide a process that favors the p-phenylenediamine product, with high yield as well as good selectivity. Furthermore, it is an object of the present invention to provide a process that produces less waste and fluvial effluents. A further objective is the production of phenylenediamine derivatives which can be used industrially as antidegradants manufactured from the high purity products resulting from the process of the present invention SUMMARY OF THE INVENTION The present invention is directed to an improved method for the preparation of substituted aromatic amines of the formula (I) which includes the following steps: a) oxidation of an aromatic amine of the formula (II) in the presence of a pentacyanoferrate complex (II) ) metal to form an arylene diaminepentacyanoferrate complex, said metal being chosen from the group consisting of potassium and sodium; and b) catalytic reduction with hydrogen of said arylene diaminepentacyanoferrate complex using a heterogeneous metal catalyst, thus producing the corresponding substituted aromatic amine of the formula (I). where n is equal to 2 to 5, and R (and R2 are defined below) Ri and R can be the same or different, they must be ortho or meta to the amino group, and they can be hydrogen, C1-C4 alkyl, C1-C4 alkoxy, halogen, cyano, carboxylate salts and carboxylic acid amides or mixtures thereof . The most preferred preparation is directed to the aniline-oxidizing process in the presence of trisodium pentacyanoferrate (I I) complexes containing various water-soluble ligands, such as ammonia, monoalkylamine, dialkylamines, trialkylamines and the like. The oxidizing agents can be oxygen or hydrogen peroxide. The N-phenyl-p-phenylene diamino pentacyano-ferrate complex is then reduced with hydrogen using a heterogeneous metallic catalyst, which may or may not be supported. Suitable supports could include those that are known in the art such as, for example, carbon or alumina. The mixture of aniline and N-phenyl-p-phenylenediamine is then extracted with a suitable solvent after filtration of the heterogeneous catalyst. The preferred solvents are harmless to the environment, immiscible with water and easily recirculated. The aqueous layer containing the pentacyanoferrate (II) complex is then recirculated.

DETAILED DESCRIPTION OF THE INVENTION A preferred method of the present invention for producing N-phenyl-p-phenylenediamine (FFDA) includes the steps of: a) oxidation of aniline in the presence of trisodium pentacyanoferrate (I I) complexes with the optional use of a heterogeneous metal catalyst; followed by b) reduction of the N-phenyl-p-phenylenediamine-pentacyanoferrate complex with hydrogen using a heterogeneous metallic catalyst. In most cases, both steps (a) and (b) will employ the same heterogeneous catalyst. In the first step, any suitable oxidant - including oxygen or hydrogen peroxide - can be used as the oxidizing agent. Oxygen is the preferred oxidizing agent. Even more preferred is the use of oxygen under pressure and at elevated temperatures, which will increase the speed of oxidation and facilitate the termination of step a. The metal complexes of pentacyanoferrate (I I) used in the present invention must be of the water-soluble type and have water-soluble ligands as part of the complex. The preferred metals are alkalines such as sodium or potassium. Most preferred, the trisodium pentacyanoferrate (II) complex containing various water-soluble ligands, is illustrative of the class of useful complexes. These ligands can be ammonia, monoalkylamines, dialkylamines or trialkylamines. A preferred structure for this preferred complex is Na3 [Fe (CN) 5NH3 »xH2?], Or its dimer. In the second step of the preferred reaction, the complex of N-phenyl-p-phenylenediamine-pentacyanoferrate is reduced with hydrogen using a heterogeneous metallic catalyst. This catalyst is selected from Group VIII of heterogeneous metals such as palladium, platinum, ruthenium, rhodium or nickel. The catalyst may or may not be supported. If supported, the supports can be carbon, alumina and the like, many of which are known to those who are familiar with the art. The mixture of aniline and FFDA that is the product of the reaction is extracted with a suitable solvent. Then the catalyst is filtered heterogeneous. Suitable solvents include those that are immiscible with water and are easily recirculated. The aqueous layer containing the pentacyanoferrate (II) complex is then recirculated. The compounds of the present invention can be advantageously synthesized using the following general method. The preferred method for the preparation of FFDA is contained in the following examples. The first step of a preferred process of the present invention includes the dissolution of sodium pentacyanoaminoferrate (II) in water. The synthesis of sodium pentacyanaminoferrate (I I) is known. It was prepared according to the method of G. Brauer in "Handbook of Preparative Inorganic Chemistry", second ed. Vol. II, Academic Press, New York, N.Y. 1965 p. 151 1.

New method for the preparation of trisodium pentacyanoferrate (II) An alternative method for the preparation of sodium pentacyanoferrate (II) is the concurrent addition of an aqueous solution of iron chloride tetrahydrate, stabilized with hypophosphorous acid, and sodium cyanide at a ratio of 1 to 5 equivalents, to an aqueous solution of sodium hydroxide. ammonium. The aqueous solution of ammonium hydroxide can contain from an equivalent based on the iron chloride to a large excess. The preferred range is from 2 to 10 equivalents and the most preferred is from 3 to 6 equivalents of ammonium hydroxide. The concurrent additions are made for one to three hours and then the solution is filtered, if necessary, to extract small amounts of iron hydroxide and the complex is precipitated by the addition of isopropanol or any other suitable water-soluble organic solvent. The complex can be dried or dissolved again in water without drying and used directly. The excess ammonia and isopropanol are recovered. For the addition of aniline, an organic solvent miscible with water can be added to help solubilize the aniline. In the present invention, this reaction can be carried out without organic solvent. Ethylene glycol, propylene glycol, diethylene glycol and triethylene glycol are examples of said solvents. 2 equivalents of aniline are added and then the mixture is oxidized. Two possible oxidizing agents that can be used are oxygen and hydrogen peroxide. A heterogeneous metallic catalyst can be added before oxidation. In the second step of the process of the present invention, the oxidized complex containing the N-phenyl-p-phenylenediamine ligand is subjected to hydrogenation in the presence of a heterogeneous metal catalyst. This can be carried out without the addition of solvent or in the presence of a suitable solvent immiscible with water. Possible solvents included in this category are butyl acetate, hexanol, 2-ethyl-1-butanol, hexyl acetate, ethyl-butyl acetate, amyl acetate, methyl isobutyl ketone or aniline and the like. After hydrogenation, the heterogeneous catalyst is removed by filtration and the organic layer is separated. The solvent, aniline and N-phenyl-p-phenylenediamine are recovered by distillation. The sodium pentacyanoaminoferrate (II) is then recirculated. The reaction is best carried out at a pH which is equivalent to the pH of the solution containing the complex dissolved in water. The pH is adjusted, when necessary, after each recirculation of the complex by adding ammonia to the solution in order to maintain the pH equivalent to the initial pH of the solution at the beginning of the process. This adjustment of the pH is achieved by the addition of an appropriate base, such as for example ammonium hydroxide or ammonia, the ligand used in the complex. The most preferred range of pH is 10 to 12. A pH equivalent to the pH of the dissolved complex, which depends on the concentration of the solution, is preferred. The pressures of oxygen and hydrogen can vary from about 1 atmosphere to 100 atmospheres. The preferred limits for these pressures would be approximately 2 to 75 atmospheres. The preferred limits for these pressures would be approximately 50 to 75 atmospheres, or 5.0 x 106 to 7.5 x 106 Nm'2. Similar pressures are used for the reduction reaction with hydrogen. Temperatures can vary to the point where the complex loses stability, which is currently believed to be from about 5 ° C to about 65 ° C in a closed system. Although the reaction can be carried out at lower temperatures, the reaction rate of the oxidation step is significantly lower. The preferred operating temperature for the oxidation reaction is between 30 ° C and 55 ° C, and the most preferred range is 45 ° C to 55 ° C. The temperature used will require a balance of factors to maximize the speed of the reaction and the performance of the process. Temperatures higher than those specified here will slowly degrade the complex. Low temperatures will reduce the solubility of the complex and the speed of the reaction. Several ligands can be used in place of ammonia in the sodium pentacyanoferrate (I I) complex. The ligands may be monoalkylamines such as methyl amine, ethyl, propyl or butyl, dyalkylamines such as dimethyl or diethyl amine and trialkylamines such as trimethyl or triethyl amine. Other amines that can be used are N. N-dimethylaminoethanol, N, N, N ', N'-tetramethylethylenediamine, and substituted or unsubstituted pyridine. A variety of other ligands can be used, limited only by their solubility and their ability to be displaced by aniline and by their stability. In the present invention, sodium pentacyanoferrates (I I) containing non-ammonia ligands were prepared by replacing the ammonia complex with an excess of the appropriate ligand. Among the heterogeneous metal catalysts that may be used are palladium-in-carbon, platinum-in-carbon, ruthenium-in-carbon, rhodium-in-carbon, and Raney nickel. Non-carbon supports can also be used, such as alumina, quiselgur, silica and the like. Noble metals are preferred among the catalysts that can be used. Even more preferred are supported noble metal catalysts. An even more preferred catalyst is platinum or palladium supported on carbon. The recirculability of the pentacyanoaminoferrate complex is demonstrated in several examples of this invention. The recirculation process can be carried out at temperatures from 25 ° C to 60 ° C, more preferably between 45 ° C and 55 ° C. The recirculability is useful with ligands other than ammonia in the pentacyanoferrate (II) complex, such as pentacyanotrimethylaminoferrate (II) complexes or pentacyanoisopropylaminoferrate (I I). The experimental details of the recirculability, including the conversion and yield data, are presented in the examples.

The reductive alkylation of FFDA to produce antidegradants can be conducted by any of several known methods to those who are skilled in the art. See, for example, Patent No. 3, 336,386 of US Pat. , which is incorporated as a reference. Preferably, FFDA and a suitable ketone or aldehyde are reacted in the presence of hydrogen and a catalyst such as for example platinum sulfide with or without support. Suitable ketones include methyl isobutyl ketone, acetone, methyl isoamyl ketone, and 2-octanone. The following examples serve to further illustrate the present invention and are not intended to limit the scope of the present invention in any way.

EXAMPLES Example 1: Oxidation of aniline using hydrogen peroxide as an oxidizing agent (step a) and hydrogen (with 5% palladium / carbon) as a reducing agent (step b) in the preparation of FFDA. The reaction of step a was carried out using 3.0 g of aniline, 6.0 g of sodium pentacyanoferrate (II), 300 ml of distilled water and 1.0 g of 5% of palladium in carbon (Pd / C) (50 g. wet%) in a three-neck flask equipped with mechanical stirrer and addition funnel. 8 ml of hydrogen peroxide ai 30% was added (oxidizing agent) for 0.5 hours. The heterogeneous catalyst was removed by filtration and the reaction mixture transferred to a 1 liter Magne-Drive autoclave.

Then, 1.0 g of the fresh Pd / C catalyst (50% water) was added. The vessel was sealed, purged first with nitrogen and then with hydrogen and pressurized with hydrogen at about 1000 psig [69 atm. or 6.9 to 106 NM "2] The vessel was stirred at room temperature for 2.0 hours, Isopropyl acetate was added to the reaction mixture after venting and purging with nitrogen, the catalyst was removed by filtration and the The organic solution was analyzed by gas chromatography using a Varian 3400 instrument equipped with a DB-1 capillary column.The product, N-phenyl-p-phenylenediamine (FFDA), was found in a conversion of 74.3%, and the aniline was measured at 18.4% The yield based on the conversion of aniline was 91%.

EXAMPLES 2-6: Oxidation of aniline using oxygen as the oxidizing agent (step a) and hydrogen with various metal catalysts as a reducing agent (step b) in the preparation of FFDA.

Using the basic procedure described in Example 1, several reactions were made in a 1 liter Magne-Drive autoclave using 38, 0 g of sodium pentacyanoaminoferrate (II), 18.6 g of aniline, 2.0 g of metal catalyst, 50.0 g of ethylene glycol and 150 g of distilled water. The metal catalysts employed in Examples 2-6 are Pd, Ru, Pt, Rh and Ni supported, respectively. In Examples 2-5, the heterogeneous catalysts are present at 5% by weight on carbon and are employed at 4.0 g and 50% water. In Example 6, the nickel is used as 50% dry Ni / quiselgur 2.0 grams. The vessel was sealed, first purged with oxygen and pressurized to 400 psig [28 atm. or 2.8 x 106 Nm "2. The vessel was stirred at room temperature for 2.5 hours After this stirring, the vessel was purged with nitrogen and then 100 ml of butyl acetate was pumped into the autoclave. The vessel was purged with hydrogen and then pressurized with hydrogen to 400 psig [28 atm. 2.8 x 106 Nm "2]. Then the vessel was stirred at room temperature for 1.0 hour. The ester solution was isolated and analyzed by H PLC. It was found that the nickel catalyst in quiselgur (Example 6) was inactive. The results of these Examples are presented in Table 1 TABLE 1 Notes for Table 1 (a) Analysis of N-phenyl-p-phenylenediamine by reverse phase HPLC using a water-acetonitrile gradient with a Perkin-Elmer 410 series LC pump, Diode Array LC 235 detector using a pecosphere ™ 3C column 18 of 3.3 cu. (b) The yield of N-phenyl-p-phenylenediamine is based on converted aniline.

Example 7: Oxidation of aniline using oxygen without metal catalyst (step a) and reduction with hydrazine (step b) in the preparation of FFDA. In a similar manner to the previous examples, step (a) of the reaction was carried out in a 1-liter Magne-Drive autoclave using 24 g of sodium pentacyanoferrate (II), 12.8 g of aniline, 100 ml of ethylene glycol and 300 g. ml of distilled water. The vessel was sealed, purged with nitrogen, then oxygen and pressurized with oxygen to 400 psig [28 atm. or 2, 8 x 106 Nm "2] .The vessel was stirred at 15-20 ° C with cooling to control the temperature for 6 hours.After oxidation, a 1 ml sample was taken out of the autoclave. Isopropyl acetate to the sample, and the synthesis of FFDA was continued with the reduction, step (b), with hydrazine The remaining mixture in the autoclave was purged with nitrogen, then hydrogen and pressurized with hydrogen to 400 psig [28 atm. or 2.8 x 106 Nm "2]. The reaction was stirred at 15-25 ° C for 1 hour. The reaction was vented and purged with nitrogen and isopropyl acetate was added. After this, the organic layer was separated. Analyzes were made by gas chromatography using a Varian 3400 G.C. equipped with a megabore DB-1 column. The conversion to N-phenyl-p-phenylenediamine (FFDA) by hydrogenation was 6%. The conversion by reduction with hydrazine was 66%. As a result of this example, it was concluded that hydrogenolysis does require a metal catalyst, while oxidation can be done without it. However, it should be noted that it may be convenient to add the heterogeneous catalyst before oxidation. The small amount of N-phenyl-p-phenylenediamine that was found could be the result of electron transfer reactions during oxidation.

EXAMPLES 8-10: Yield of oxidation reactions (step a) and reduction (step b) to produce FFDA under a variety of pressures. The reactions of these examples were made in a manner similar to those described above. In a 1-liter Magne-Drive autoclave using 76.0 g of 3 different batches of sodium pentacyanoferrate (II), 37.2 g of aniline, 4.0 g of 5% Pd / C catalyst, 100 g of Ethylene glycol and 300 g of distilled water. The vessel was sealed, first purged with oxygen, then pressurized with oxygen to the desired pressure. The vessel was stirred at room temperature for 2.5 hours.

After this oxidation, the vessel was first purged with nitrogen. Butyl acetate (200 ml) was pumped into the autoclave, which was then purged with hydrogen, and then pressurized with hydrogen to the desired pressure. The vessel was stirred at room temperature for 1.0 hour. After separation of the organic layer in the normal manner, analyzes by H PLC produced the conversions presented in Table 2.

TABLE 2 Notes for Table 2: In column 2, the pressures shown are for both oxygen and hydrogen. (a) Performance based on aniline used.

EXAMPLES 11 AND 12: Demonstration of the recirculation capacity of the sodium pentacyanaminoferrate (II) complex. In accordance with the above examples, the reaction was carried out in a 1 liter Magne-Drive autoclave using 76.0 g of sodium pentacyanoferrate (II), 37.2 g of aniline, 8.0 g of Pd / C catalyst at room temperature. %, 100 g of ethylene glycol and 300 g of distilled water. The vessel was sealed, first purged with oxygen and pressurized with oxygen to 400 psig [28 atm. or 2.8 x 106 Nm "2] The vessel was then stirred at room temperature for 2 hours., 5 hours. After oxidation, the vessel was first purged with nitrogen followed by the addition of 200 ml of butyl acetate pumped into the autoclave. Then the autoclave was pressurized with hydrogen to 400 psig [28 atm. or 2.8 x 10ß Nm "2] The autoclave was stirred at room temperature for 1.0 hour The autoclave was opened, the solution was filtered to extract the metal catalyst, and the layers were separated. it was analyzed by gas chromatography, and the aqueous layer was put back into the autoclave.At this time 37.2 g of aniline and 8.0 g of 5% Pd / C catalyst were added, then the vessel was sealed, purged first with oxygen and pressurized with oxygen up to 400 psig [28 atm. or 2.8 x 106 Nm'2] .The mixture was stirred at room temperature for 2.5 hours, and then purged with nitrogen. pumped 200 ml of butyl acetate into the autoclave.The vessel was then purged with hydrogen and pressurized with hydrogen to 400 psig [28 atm or 2.8 x 106 Nm'2] .The mixture was stirred at room temperature for 1.0 hour, the ester solution was analyzed by gas chromatography. Lysis of both fresh (example 11) and recirculated (example 12) material are shown in Table 3 in terms of conversion and yield.

TABLE 3 (a) GC analysis using a Perkin Elmer Model 8310 gas chromatograph with a 1 meter SP 2100 column, (b) Based on converted aniline.

EXAMPLES 13-15: Use of ligands other than ammonia for the pentacyanoferrate (II) complex and the recirculation. According to the above examples, the reaction was carried out in a 1 liter Magne-Drive autoclave using 42.8 g of sodium pentacyanotrimethylaminoferrate (II), or the same amount of sodium pentacyanoisopropylaminoferrate (II), 18.6 g of aniline, 4.0 g of 5% Pd / C catalyst, and 200.0 g of distilled water. The vessel was sealed, first purged with oxygen and pressurized to 250 psig [18 atm. Or 1, 8 x 106 Nm'2] with oxygen. The vessel was then stirred at room temperature for 0.5 hours. After oxidation, the vessel was first purged with nitrogen followed by the addition of 200 ml of butyl acetate pumped into the autoclave. Then the autoclave was pressurized with hydrogen to 400 psig [28 atm. or 2.8 x 106 Nm'2. The autoclave was stirred at room temperature for 1.0 hour.

After stirring, the autoclave was opened and its contents extracted. Then the mixture was filtered and the aqueous and organic layers separated. The ester solution, contained in the organic layer, was analyzed by gas chromatography using a Perkin-Elmer Model 8310 Gas Chromatograph with a 1-meter SP2100 column, and the aqueous layer was again placed in the autoclave. At this time, 18.6 g of aniline and 4.0 g of 5% Pd / C catalyst were added. Then the vessel was sealed, first purged with oxygen and pressurized with oxygen to 250 psig [18 atm. or 1.8 x 106 Nm "2] .The vessel was stirred at room temperature for 3.0 hours, followed by pumping 100 ml of butyl acetate into the autoclave.The vessel was first purged with nitrogen and then hydrogen and pressurized with hydrogen to 250 psig [18 atm or 1, 8 106 Nm "2]. The vessel was stirred at room temperature for 0.5 hour, after which the autoclave was opened and the contents extracted. The ester solution was analyzed by gas chromatography, using the same equipment that has been specified in the previous examples. The results of the analyzes are presented in Table 4.

TABLE 4 Notes for Table 4: (a) Performance based on aniline used.

EXAMPLES 16-17: Use of a non-noble metal catalyst in the reduction (step b), in the preparation of FFDA. According to the previous examples, the reaction was carried out in a 1 liter Magne-Drive autoclave using 57 grams of sodium pentacyanotrimethylaminoferrate (I I), 27.9 g of aniline, and 250 ml of distilled water. The vessel was sealed, first purged with oxygen and pressurized with oxygen to 250 psig [18 atm. or 1, 8 x 106 Nm'2]. The vessel was then stirred at room temperature for 3 hours. After this oxidation, the vessel was first purged with nitrogen, then opened and the catalysts were added. Then the butyl acetate (200 ml) was added. The vessel was sealed, and then pressurized with hydrogen to the desired pressure of 400 psig [28 atm. or 2, 8 x 106 Nm'2]. The catalysts used for the reduction, step b, were those shown in Table 5. The vessel was stirred at room temperature for 1.0 hour. The ester solution was analyzed by gas chromatography, using the same equipment that has been specified in the previous examples. The results of the analyzes are presented in Table 5.

TABLE 5 (a) Yield based on moles of aniline used.

In view of the many changes and modifications that can be made without departing from the principles on which the present invention is based, reference should be made to the appended statements to achieve an understanding of the scope of the protection afforded to the invention.

Claims (20)

1 - . 1 - A method for the preparation of substituted aromatic amines of the formula (I) which includes the steps of: (a) oxidation of a solution of an aromatic amine of the formula (II) in the presence of an oxidizing agent and a metallic pentacyanoferrate (II) complex to form an arylene diaminepentacyanoferrate complex, said metal being chosen from the group consisting of potassium and sodium; and (b) the catalytic reduction of said arylene diaminepentacyanoferrate complex with hydrogen using a heterogeneous metal catalyst, thus producing the corresponding substituted aromatic amine of the formula (I) wherein n is equal to 2 to 5, and R, and R2 are defined below; R t and R 2 may be the same or different, they must be ortho or meta to the amino group, and may be hydrogen, C 1 -C 4 alkoxy C 1 -C 4 alkoxy, halogen, cyano, carboxylates salts and carboxylic acid amides or mixtures thereof . 2. The method of claim 1, wherein the oxidizing agent is oxygen or hydrogen peroxide. 3. The method of claim 2, wherein the oxidizing agent is oxygen and a heterogeneous metallic catalyst is present during the oxidation step. 4. The method of claim 2, wherein the oxygen used is under pressure from about 1 to 100 atmospheres. The method of claim 2, wherein the oxygen in the oxidation step and the hydrogen in the reduction step are employed under independently chosen pressures and ranging from about 2 to 75 atmospheres. The method of claim 1, wherein the metal pentacyanoferrate (I I) complex is a trisodium pentacyanoferrate (I I) complex containing water-soluble ligands selected from the group consisting of ammonia, monoalkylamines, dialkylamines, trialkylamines, N. N-dimethylaminoethanol, N. N. N'N'-tetramethylethylenediamine and pyridine. The method of claim 6, wherein the trisodium pentacyanoferrate (I I) complex has the structure: Na3 [Fe (CN) sNH3 »xH2O], or its dimer. The method of claim 1, wherein the heterogeneous metal catalyst is a supported or unsupported catalyst selected from the group consisting of palladium, platinum, ruthenium, rhodium or nickel. 9. The method of claim 8, wherein the catalyst is platinum or palladium. 10. A method for the production of N-phenyl-p-phenylenediamine which includes the steps of: a) oxidation of aniline in the presence of an oxidizing agent and a trisodium pentacyanoferrate (II) complex to form an N-complex. phenyl-p-phenylenediaminepentacyanoferrate; and b) catalytic reduction of the N-phenyl-p-phenylenediaminepentacyanoferrate complex with hydrogen using a heterogeneous metal catalyst to produce N-phenyl-p-phenylenediamine. eleven . The method of claim 10, wherein an organic solvent miscible with water is added to solubilize the aniline and is selected from the group consisting of ethylenic giicoi, propylene glycol, diethylene glycol, triethylene glycol, and mixtures thereof. The method of claim 10, wherein the N-phenyl-p-phenylenediaminepentacyanoferrate complex is subjected to hydrogenation in the presence of a heterogeneous metal catalyst in the presence of a solvent immiscible with water selected from the group consisting of butyl acetate, hexanol,

2-ethyl-1-butanol, hexyl acetate, ethyl-butyl acetate, amyl acetate and substituted or unsubstituted aniline. The method of claim 1, which also includes the steps of: (b) recovering the metal pentacyanoferrate (II) complex that was reformed during the reduction step; and (c) recirculating said complex by repeating step (a) of oxidation using the recovered metal pentacyanoferrate (I I) complex. The method of claim 1, wherein said oxidation step is conducted in an aqueous medium. 15. The method of claim 1, wherein said oxidation step (a) takes place at a temperature ranging from about 40 ° C to 60 ° C and said step (b) of reduction has a reaction temperature ranging from about 5 ° C to 60 ° C for the reaction with hydrogen. 16. A method of producing trisodium pentacyanoferrate (II) which includes the steps of: (a) the concurrent addition of an aqueous solution of iron chloride tetrahydrate, stabilized with hypophosphorous acid and sodium cyanide at a ratio of 1 to 5 equivalents, an aqueous solution of ammonium hydroxide to form a reaction mixture; and (b) separating said trisodium pentacyanoaminoferrate (I I) from said reaction mixture. 17. A method according to claim 16, wherein the aqueous solution of ammonium hydroxide may contain from 1 to 10 equivalents of ammonium hydroxide based on the iron chloride tetrahydrate. 18. A method according to claim 16, wherein said separation step is made by the addition of a water-soluble organic solvent to said reaction mixture, thereby initiating the precipitation of the trisodium pentacyanoferrate (II) from said reaction mixture. The method of claim 1, wherein the pH of the reaction ranges from 10 to 12. The method of claim 1, wherein the pH of the reaction is maintained substantially at a pH equivalent to the solution of the metal pentacyanoferrate (II) complex dissolved in water.