WO1997018035A1

WO1997018035A1 - Oxidation process of organic substrates in the presence of metal complexes of tetra-, penta- and hexacoordinating ligands, and oxidation catalysts containing them

Info

Publication number: WO1997018035A1
Application number: PCT/FR1996/001804
Authority: WO
Inventors: Laurent Fraisse; Jean-Jacques Girerd; Frédéric Perie; Alain Rabion; David Tetard; Jean-Baptiste Verlhac; Alexander Nivorozhkin
Original assignee: Elf Aquitaine
Priority date: 1995-11-16
Filing date: 1996-11-15
Publication date: 1997-05-22
Also published as: NO982240L; NO982240D0; EP0914205A1; FR2741340B1; AU7628996A; CA2235764A1; FR2741340A1; JP2000500151A

Abstract

Selective oxidation process for organic substrates by contacting said substrates with an oxidant selected amongst hydroperoxides and/or hydrogen peroxide in the presence of a catalyst containing a metal complex of a least one multicoordinating nitrogenated ligand characterized in that the molar ratio metal complex/peroxide is comprised between 1 and 10-10, the temperature is lower than 120 °C, and the metal complex has the general formula: [L¿x? My Xu]?z Y¿q with M a manganese or iron atom in oxidised condition, X a bridge between metals, Y a counter-ion, x and y being » 1, 0 « u « 3, z being the charge of the metal complex and q = z/charge of Y, and L is a ligand having the formula: R1 Ar1 N - (CH2)r - N Ar2 R2, with Ar1 and Ar2 being linear C1 to C6 carbon chains, linked to a nitrogenated heterocycle, R1 and R2 being hydrogen or a C1-C6 alkyl chain optionally connected to a nitrogenated heterocycle, 2 « r « 4.

Description

PROCESS FOR THE OXIDATION OF ORGANIC SUBSTRATES IN THE PRESENCE OF METALLIC COMPLEXES OF TETRA-, PENTA- AND HEXACOORDINANTS AND OXIDATION CATALYSTS CONTAINING THEM

The present invention relates to a process for the oxidation of organic substrates by means of hydroperoxides and / or peroxides in the presence of metal complexes with tetra-, penta- and hexacoordinating ligands in organic and / or aqueous media, and the catalysts of oxidation containing these complexes. It relates more particularly to the oxidation of organic substrates such as saturated hydrocarbons, cyclic or not, branched or not, optionally comprising heteroatoms, unsaturated, aromatic and polyaromatic hydrocarbons in the presence of iron and manganese complexes. The oxidation of these organic substrates aims either to modify their polarity and their solubility in order to facilitate their biodegradation by microorganisms, or to transform them chemically with a view to using them as such or for their reactivity in certain specific reactions such as the oxidation of cyclohexane to cyclohexanol / cyclohexanone, first step in the synthesis of adipic acid, a key monomer in the synthesis of nylon.

For polyaromatic compounds which are known to be harmful to human health, we seek to facilitate their biodegradation by reducing their aromaticity by opening cycles or by introducing oxides or hydroxides groups on the cycle which are more easily accessible to biodegrading products.

To oxidize certain saturated organic substrates, it is known to use nonhemic enzymes containing iron, among which are methane monooxygenase or MMO which catalyzes the conversion of methane to methanol. This type of enzyme is particularly interesting because of the presence in its structure of oxygen bridges between two complexed iron atoms, these bridges being recognized as favorable to this oxidation. Likewise, for the oxidation of DNA, the reaction is catalyzed by an iron complex pentacoordmé by bleomycme via the nitrogen atoms of the latter.

As the stability of these enzymes is limited, it is advantageous to reproduce their active functions in the oxidation reactions of organic substrates in the presence of hydroperoxides or hydrogen peroxide or any other well-known oxidant. Thus, we will focus on chemical complexes with a structure close to that of the active sites of these enzymes.

To oxidize aromatic, phenol and polyaromatic compounds, it is known to use metalloporphyrm and metallophthalocyanm complexes of iron and manganese which, in solution or supported by a resin, in the presence of hydrogen peroxide and / or sodium persulfates and potassium in aqueous solution make it possible to introduce into the molecule qumonic and qumoleic groups or acid groups after breaking at least one cycle (French patent FR 2,650,761 and French patent application FR 2,716,676).

To oxidize saturated organic compounds, certain manganese complexes with N, N'-Bιs- (2-pyridylmethyl) ethane-1, 2-dιamme or Bispicen as described by Chi-Ming Che, Wai-Tong Tang, Kwok- Ym Wong, Wing-Tak Wong and Tmg-Fong Lai in J. Chem. Reseach, 5, 1991, p30 are known to transform cyclohexane into cyclohexanone or cyclohexanol in the presence of terbutylhydroperoxide or isodosylbenzene in acetonitrile medium, possibly in the presence of carbon tetrachloride.

Similarly, the tris (2-pyridylmethyl) amine or TPA complex with iron, very often cited in the literature allows a similar oxidation in the presence of terbutylhydroperoxide (see A. Leising, J. Kim, MAPérez and L. Que, Jr , J. Am. Chem. Soc, 1993, 115, 9524-9530) However, if a number of manganese and iron complexes have been studied in terms of crystal structure and stability, it can be seen that few of them have been tested as a catalyst for the oxidation reactions of organic substrates and that none of them is universally effective for all types of organic substrates.

The present invention therefore relates to a process for the oxidation of organic substrates in the presence of active oxidants in redox reactions and to metal complexes obtained by complexation of transition metals with multicoordinating ligands with nitrogen endings. This process aims to obtain smaller and more polar molecules, especially for the production of compounds with high added value, or molecules of lower molecular weight and easier to biodegrade by the techniques in use.

The present invention therefore relates to a process for the selective oxidation of organic substrates by bringing said substrates into contact with an oxidant chosen from hydroperoxides and / or hydrogen peroxide in the presence of a catalyst formed from at least one complex. metal of at least one multidentate ligand nitrogen with at least one transition metal, by operating in an aqueous diluent and / or organic, characterized in that the molar ratio metal complex / peroxide is between 1 and IO ^"1 ^ and temperature is less than 120 ° C, and in that the metal complex has a general formula (I) corresponding to:

[L _x M _y X _u ] ^z Yq ⁽ D in which M is a metal from the group consisting of manganese and iron in at least one of the possible oxidation states II, III, IV or V, X is a bridging species metals selected from the group consisting of water, hydroxide ions OH ^~ , oxygen ions O ^2- , 02 ^{2 ~} and O2 ^" , sulfur ions S ^2- , peroxide ions HOO", carboxyl ions RCOO ^" , R being an atom hydrogen, an optionally substituted alkyl or aryl group, and the sulphate, phosphate, carbonate and halide ions,

Y is a counterion chosen from the group consisting of halides, chlorates, borates, sulfates, phosphates, nitrates, perchlorates, sulfonates, triflates and hexafluorophosphate, with x and y denoting numbers integers greater than or equal to 1, u denoting an integer varying from 0 to 3, z denoting an integer corresponding to the charge of the metal complex and q being equal to the ratio of z to the charge of Y, and finally, L is a ligand chosen from the ligands of formula (II) below:

in which Ar _] _ and Ar _{2, which are} identical or different, each consist of a linear carbon chain containing from 1 to 6 carbon atoms linked to at least one heterocycle comprising at least one nitrogen atom, optionally protonated, Rτ_ and R ₂ being identical or different and representing groups consisting of the hydrogen atom or a linear or branched alkyl chain containing from 1 to 6 carbon atoms optionally linked to at least one heterocycle comprising at least one nitrogen atom, optionally protonated, and r denotes an integer varying from 2 to 4,

In the context of the present invention, the organic substrates are present in solution, in suspension or in emulsion in a medium inert to oxidation, organic, aqueous or semi-aqueous such as for example a water / acetonitrile mixture or a water / dichloromethane. These oxidizable substrates are compounds of the group consisting of linear or branched alkanes, cyclic alkanes, linear alcohols or branched and aromatic, diaromatic and polyaromatic compounds optionally containing a heteroatom other than oxygen.

In the present invention, the preferred complexes are obtained from tetra-, penta- and hexacoordinating ligands comprising aromatic nitrogen heterocycles, these ligands containing from 4 to 6 nitrogen atoms capable of coordinating with the same metal by at least three of these nitrogen atoms. According to a first form of the invention, Ar ^ and Ar ₂ correspond in the ligand of formula (II) to one of the formulas (III), (IV) and (V) below:

or

or

N CH

CH2) _r , -C II (V) ^p \ N CH

R "with p denoting an integer varying from 1 to 6 and R ′ and R" representing the hydrogen atom, an alkyl group comprising from 1 to 6 carbon atoms, a halogen atom or one of the nitro or methoxy groups and ethoxy.

It would not depart from the scope of the invention if in the above formulas, the same cycle associated with a benzenic cycle, that is to say its benzopyridyl or benzimidazolyl counterpart, was substituted for the cycle presented.

In a first embodiment of the process according to the invention, the iron or manganese complexes are obtained from tetracoordinated ligands with at least one metal atom, such as in formula (II), R ^ and R ₂ are either hydrogen or identical or different alkyl groups comprising from 1 to 6 carbon atoms and preferably 1 to 3 carbon atoms.

Among the different complexes according to this first mode, the complexes of N, N '-Bis- (2-pyridylmethyl) ethane-1,2-diamine or Bispicen, of N, N' -dimethyl-N, N '-Bis- ( 2- pyridylmethyl) ethane-1,2-diamine or Bispicen (NMe) ₂ and N-

N '-dimethyl-N, N' -Bis- (1-methylimidazol-2-yl-methyl) ethane-1,2-diamine or (1Me) Bisim (NMe) ₂ with iron and / or manganese are preferred.

The process according to the invention is particularly effective in the presence of a complex comprising at least one metal-ligand system with tetracoordination of the metal by the ligand chosen from the group consisting of Fe-Bispicen, Mn- Bispicen, Fe-Bispicen (NMe) ₂ , Mn-Bispicen (NMe) ₂ , Fe- lMeBisim (NMe) ₂ , Mn-lMe-Bisim (NMe) ₂ , Fe-lMeBisim, Mn- lMeBisim, two coordinated metals that can be joined together by μ-oxo or μ bridges -carboxylato. The presence of alkyl and preferably methyl groups on the nitrogen atoms of the diamine chain promotes the stabilization of the complexes obtained with these ligands.

In a second embodiment of the process, the iron and manganese complexes are obtained from pentacoordinating ligands such that in formula (II), R- ^ is a group consisting of a hydrogen atom or a linear alkyl chain or branched containing from 1 to 3 carbon atoms, R ₂ , Ari and Ar ₂ are identical and correspond to one of the formulas (III), (IV) or (V) in which the heterocycle is optionally substituted benzopyridyl or benzimidazolyl counterpart.

In this second embodiment according to the invention, the preferred metal-ligand system is obtained by complexation of iron or manganese with N, N, N '-Tris- (2-pyridylmethyl) -N' - methylethane-1, 2- diamine or TrispicMeen, also called Fe-TrispicMeen or Mn-TrispicMeen.

In a third embodiment of the process, the iron and manganese complexes are obtained from hexacoordinating ligands of formula (II) in which Ri and R ₂ consist, as Ari and Ar _2, of an alkyl chain comprising from 1 to 4 carbon atoms, linked to a nitrogen heterocycle. In a first particular form of this third mode, Ri, R ₂ , Ari ^{and Ar} 2 ^are identical and correspond to one of the formulas (III), (IV) or (V) in which the heterocycle has optionally been replaced by its benzopyridyl or benzimidazolyl counterpart. In this third preferred embodiment of the invention, the preferred ligand is N, N, N ', N' -tetrakis- (2-pyridylmethyl) ethane-1,2-diamine or TPEN and the preferred iron and manganese complexes are the complexes of the metal-ligand systems Fe-TPEN and Mn-TPEN. To carry out the invention, the oxidation reactions preferably take place in an inert oxidation, organic, aqueous or semi-aqueous medium such as, for example, water / acetonitrile and water / dichloromethane mixtures, in the presence of peroxide. hydrogen or terbutylhydroperoxide.

The metal complexes are used in solution or supported on inert solids with regard to the oxidation reaction, in particular on resins, silica clays, active charcoal or wool residues. They can be either impregnated or linked by a covalent chemical bond with an element of the support, in particular by grafting on the support or even by insertion into a metallic network such as silicic networks. A second object of the invention is the application according to the invention to the gentle oxidation of substrates with a view to the specific production of products with high added value such as alcohols, aldehydes and ketones, characterized in that the ratio initial oxidative / substrate molar is preferably less than 0.5.

A third object of the invention is the application of the method according to the invention to the oxidation of substrates with a view to their biodegradation, characterized in that the ratio initial oxidant / substrate molar is greater than or equal to 0.5, and preferably greater than 1 for the degradation of polyaromatics.

In addition, the present invention also relates to oxidation catalysts present in aqueous, semi-aqueous or organic solution, supported or not supported on a solid inert to oxidation, containing iron and / or manganese complexes characterized in that the said metal complex has the general formula (I) corresponding to:

[L _x M _y X _u ] ^z Y _q (I) in which M is a metal from the group consisting of manganese and iron in at least one of the possible oxidation states II, III, IV or V, X is a bridging species of metals chosen from the group consisting of water, hydroxide ions OH ^" , oxygen ions O ^2- , 0 ₂ ² " and 0 ₂ ^~ , sulfur ions S ^{2 "} , peroxide ions HOO ^~ , carboxylated ions RCOO ^" , R being a hydrogen atom, an optionally substituted alkyl or aryl group, and the sulphate, phosphate, carbonate and halide ions,

Y is a counterion of the group consisting of halides, chlorates, borates, sulfates, phosphates, nitrates, perchlorates, sulfonates, triflates and hexafluorophospate, with x and y denoting whole numbers or equal to 1, u denoting an integer varying from 0 to 3, z denoting an integer corresponding to the charge of the metal complex and q being equal to the ratio of z to the charge of Y, and L a ligand of formula (VIII ) below:

in which s represents an integer varying from 2 to 6, Ari, ^Ar 2 ^{and Ar} 3 ^are identical or different and each consist of a linear carbon chain containing from 1 to 6 carbon atoms linked to at least one heterocycle comprising at least one nitrogen atom optionally protonated, Ri denoting a group consisting of a hydrogen atom or a linear alkyl chain or branched containing from 1 to 6 carbon atoms, optionally connected to at least one heterocycle comprising at least one nitrogen atom, optionally protonated, the ratio of the number of ligand molecules L to the number of metal atoms of the complexed ion , or x / y, being between 0.5 and 5 and preferably between

0.5 and 2.

Preferably, Ari, Ar ₂ and Ar3 correspond to one of the formulas below:

or

or

N- CH

- (CH2) ₀ -CS (V)

; .N - CH

R 'with p representing an integer varying from 1 to 6 and, R ¹ and R "being the hydrogen atom, an alkyl group comprising from 1 to 3 carbon atoms or a halogen atom, and in which has optionally replaced the heterocycle with its benzopyridyl or benzimidazolyl counterpart.

The oxidation catalysts according to the invention preferably contain complexes of iron and manganese, each ligand being coordinated with at least one metal atom in at least one of the possible oxidation states II, III, IV or V, by at least three of its nitrogen atoms, the first two coming from the diamine chain, the others, from nitrogen atoms of the nitrogen heterocyles.

Preferably, two metal atoms are linked by a chemical bridging of the group constituted by the ligand (s), the μ-oxo, μ-carboxylato and hydroxo bridges.

In a first form of these catalysts according to the invention, the iron or manganese complexes are obtained with a ligand comprising five coordination sites, of formula (VIII) in which s is equal to 2, RI is a group consisting of a hydrogen atom or a linear or branched alkyl chain containing from 1 to 3 carbon atoms, Ari, Ar2 and Ar3 are identical or different and correspond to one of the formulas (III), (IV) or (V).

In a first preferred embodiment of the invention, the heterocycles Ari, Ar2 and Ar3 are identical and of formula (III).

Among these complexes, complexes resulting from the coordination of N, N, N '-tris- (2-pyridylmethyl) -N' -methyl-ethane-1,2-diamine or TrispicMeen with iron or manganese are preferred.

In a second preferred embodiment of the invention, the heterocycles Ari, Ar2 and Ar3 are identical and of formula (IV), with p preferably equal to 1.

In a third preferred embodiment of the invention, the heterocycles Ari, Ar2 and Ar3 are identical, of formula (V) with p preferably equal to 1.

In a second form of these catalysts according to the invention, the iron or manganese complexes are obtained with a ligand comprising at least six coordination sites, of formula (VIII) in which Ri corresponds as Ari, ^Ar 2 ^{and Ar} 3 ^ one of the formulas (III), (IV) and (V) in which p varies between 1 and 6. In a first preferred mode, in the ligand of formula (VIII), s is equal to 2, Ri, Ari, ^Ar 2 ^and Ar3 are identical to formula (III) and p is 1 or 2. Thus, complexes resulting from the coordination of N, N, N ', N' -tetrakis- (2-pyridylmethyl) ethane-1,2-diamine or TPEN with iron and manganese are preferred.

In a second preferred mode, in the ligand of formula (VIII), s is equal to 2, Rj_, Ari, ^Ar 2 ^and Ar3 are identical to formula (IV) and p is equal to 1 or 2.

In a third preferred mode, in the ligand of formula (VIII), s is equal to 2, R _lr Ari, ^Ar 2 ^{and Ar} 3 are identical to formula (V) and p is equal to 1 or 2. ⁰ In order d 'Illustrate the invention, examples are given below without limitation.

EXAMPLE 1

The present example aims to show the effectiveness of the process according to the invention with regard to the controlled oxidation of alkanes into products with high added value such as alcohols, aldehydes and / or ketones.

To oxidize these alkanes according to the process of ⁽ - ¹ the invention, one operates in acetonitrile solution, these products being insoluble in water, in air and at room temperature, ie approximately 25 ° C. Different tests were carried out with different types of iron and manganese complexes according to the invention and for three cyclic alkanes, cyclohexane, cyclooctane and adamantane The major oxidation products of cyclohexane are cyclohexanone, cyclohexanol and cyclohexylterbutylperoxide. For cyclooctane, the majority oxidation product is cyclooctanone while for 0 1 adamantane, these are adamantone, and the two alcoholic forms adamantane-loi and adamantane-2ol.

Measuring the formation of these oxidation products by gas chromatography by comparing the retention times of these products with those of ^five reference products, the assay being performed by the internal standard method.

Table 1 below collates the yields obtained for each oxidation reaction after a time of reaction between 0.5 and 24 hours for each oxidation product, in ketone or aldehyde, in alcohol or in peroxide, and the total oxidation yield For the conversion of an alkane molecule to ketone or aldehyde in the presence of terbutylhydroperoxide or TBHP, it was assumed that the reaction consumed 2 moles of TBHP, while for conversion to alcohol, it consumed 1 mole of TBHP. Thus, the yields in Table I are given in molar percent: they correspond to the ratio of the number of moles of product formed to the number of moles of starting oxidizing product, this ratio being multiplied by 2 for the yields of ketone or aldehyde In the case Particular for TBHP, the total yield (RDT) of oxidation product is calculated according to the formula below:

100 [(ROH) + 2 (RC = 0) + (ROOTBHP)]

RDT =

(TBHP)

(ROH), (RC≈O), (ROOTBHP) and (TBHP) corresponding to the respective number of moles in alcohol, ketone or aldehyde, peroxide and TBHP.

In tests 1 to 10 and 15 to 21, the complexes were isolated in the solid state as described in the procedures described in A. Leismg, J. Kim, MA Pérez and L. Que, Jr, J.Am.Chem Soc, 1993, 115.9524-9530 and in French patent application No. 94.12294 of October 24, 1994.

In tests 11 to 14, the metal complexes were prepared by mixing in 5 ml of acetonitrile 8 μmoles of manganese perchlorate Mn (0104) 2 or of iron perchlorate Fe (0104) 3 with 8 μmoles of ligand.

Tests from 1 to 8 were carried out by introducing into 5 ml of acetonitrile, the equivalent of 3.75 μmol of manganese complex [LMn (μoxo) ₂ MnL] ³⁺ , 3CIO4 ^" , 3.75 mmol of substrate, 75 mg of anisole (internal standard not degraded during oxidation reactions) and 0.66 mmol of ter butylhydroperoxide (TBHP) at 86% in water. Test 9 was carried out as in test 2 but adding 33.4 μmol of sodium acetate to the solution.

Tests 10 to 14 were carried out as for tests 1 to 8, but by varying the nature of the ligand L and the method of preparation of the metal complex.

For test 15, cyclohexane was replaced under the conditions of test 2 by 0.15 mmol of adamantane. In this test, only 20.9 mg of internal anisole standard and 0.66 mmol of TBHP are used. In the case of adamantane, the main oxidation products are adamantane-2-one (ketone) and two alcohols, adamantane-1- ol (in the alcohol column of table 1) and adamantane- 2- ol (yield given in the peroxide column)

For test 16, the procedure is as for test 15 but the adamantane is replaced by 0.15 mmol of cyclooctane.

For tests 17 to 21, the manganese complex is replaced in test 1 by an iron complex of formula [LFe (μoxo) (μOAc) FeL] ³⁺ , 3CIO4 ^{4 "} , with ligand L of the substituted bispicen and unsubstituted, or alternatively substituted Bisim, the substrate to be oxidized being cyclohexane.

TBHP oxidant from tests 17, 18 and 19 is replaced by

1 'Iodosobenzene or PhlO in test 20 and with hydrogen peroxide (H ₂ 0 ₂ ) at 30% in aqueous solution in the test

21.

BOARD

TABLE I (CONTINUED)

a) R- ₎ and R ₂ in formula (II) b) α: β, α = the substituents of the heterocycle in position 4 of the pyridinyl rings or in position 1 of the imidazolyl rings β ≈ Ri and R ₂ in the formula (II) c) complex of test 2 placed in the presence of acetate ions d) yield of Adamantane-2-ol

10 ^* ) complex formed but not isolated in the solid state If, for the same substrate with the same oxidant, a catalytic activity of the complexes used is obtained for tests 1 to 8, this is no longer the case after an additional addition of oxidant. Indeed, it has been found that the catalytic activity of the complex of test 1 decreases by about 30%, the complex being probably destroyed progressively, while it remains stable for all the complexes of tests 2 to 8. The presence of substituents on the nitrogen atoms of the diamine chain promotes the stability of the complexes according to the invention.

It has also been found that it is possible to increase the kinetics of the catalytic reaction in the presence of complex [LMn (μoxo) ₂ MnL] by adding acetate ions to the reaction medium.

In tests 10 to 14, the ligands of the manganese complexes studied have a structure different from that of substituted or unsubstituted Bispicens. In particular, their catalytic activity can vary from 0 for N, N, N '(2-pyridmylmethyl) N' -methylpropane-1, 2-diamine or Trispipen to 37% for N, N, N '(2-pyridinylmethyl) N '-methyl ethane-1,2-diamine or TrispicMeen for a difference in chain length of the diamine of 1.

By comparing test 2 with tests 15 and 16, it can be seen that these complexes can also be active on other substrates such as adamantane and cyclooctane, although the bispicen complexes are probably not the most active. to oxidize them. Note, however, the selectivity of the oxidation of cyclooctane to cyclooctanone by such complexes.

Tests 17 to 21 show the effectiveness of the complexes

Iron / Bispicen with regard to the oxidation of cyclohexane. In particular, it can be seen that the oxidation of such a substrate to cyclohexanol in the presence of hydrogen peroxide is possible. EXAMPLE 2

The present example aims to show the effectiveness of the process of the invention with regard to the oxidation of alcohols into products with high added value such as aldehydes and ketones.

To oxidize these alcohols, the procedure is as in Example 1, in air, in acetonitrile medium in the presence of manganese or iron complexes obtained according to the procedure described in Example 1. The results of these tests are given as above in yield of oxidized products with respect to the oxidant. These results are collated in Table 2 below. Tests 22 to 24 are obtained under the same conditions as in test 2 of Example 1, but by substituting 2.5 mmol of benzyl alcohol with cyclohexane

(test 22) or 2.5 mmol of cyclohexanol (tests 23 and 24), the manganese complex being formed with the bispicen ligand (NMe) ₂ . Test 24 was carried out in the absence of oxidant but in air.

Tests 25 to 27 were carried out by replacing the manganese complexes with iron complexes in the procedure of test 17 of Example 1. Tests 26 and 27 were not carried out in solution in acetonitrile but in aqueous solution, to oxidize cyclohexanol (26) and 2-butanol (27) respectively, the oxidant TBHP being used at 70% in water.

TABLE I I

has substituents on the nitrogen atoms of the diamine chain and reaction in an aqueous medium and tBuOOH is concentrated to 70% in water It can be seen from this table that these oxidation systems make it possible to oxidize secondary alcohols and benzyl alcohols selectively to aldehyde and ketone. This oxidation cannot be done simply in the presence of air, which requires the presence of an oxidant such as TBHP, or H ₂ 0 ₂ , as demonstrated by tests 23 and 24.

By comparing tests 23 and 26, it can be seen that for substrates which are sufficiently soluble in water, the catalysts according to the invention are also effective in aqueous solution, which advantageously avoids the use of potentially polluting organic solvents such as than acetonitrile.

EXAMPLE 3

The present example aims to emphasize the effectiveness of the process according to the invention with regard to the oxidation of aromatics, in particular polyaromatics or PAHs which are more difficult to oxidize and therefore to biodegrade.

The tests are carried out on two model compounds of these polyaromatics which are phenanthrene and fluoranthrene. The oxidation products of these compounds and of polyaromatic compounds in general are obtained by the opening of aromatic rings and the appearance of hydroxyl or oxidized groups in the chemical structure. The disappearance of these substrates and the appearance of the oxidation products are monitored by HPLC liquid chromatography on a C18 reverse phase column (125 × 4.6) with isocratic elution with an acetonitrile / water mixture 60/40, and the pH of the reaction medium is measured at the start and end of the oxidation reaction.

The tests are carried out in an aqueous medium, the polyaromatics or substrates being present in emulsion in water, 50 μM of complex and 30 mM of hydrogen peroxide. Table III below collates the results obtained after one hour of reaction. In the case of iron complexes, the operation is carried out at a temperature of 40 ° C. for a concentration of 112 μM of phenanthrene or of fluoranthrene.

For the tests with manganese complexes, the operation is carried out at 80 ° C., the phenanthrene concentration being 561 μM.

TABLE III

FeCI ₃ , FeS04, Fe (CI0 ₄ ) ₃ and MnS0 ₄ are controls taken alone

TPA = tris (2-pyrιdylméthyl) amène TACN = 1, 4,7 bimethyl - 1, 4,7 - tπazacyclononane Trispipen = N, N, N '- Tris (2-Pyrιdylméthyl) -N' methylpropane - 1, 3 - diamine ^* complexes formed but not isolated in the solid state

It can be seen that if the reaction medium has an alkaline or neutral pH at the start of oxidation, it decreases very strongly during oxidation to become acid, this drop translating the appearance of acid carboxylic functions with respect to the starting substrates and therefore the opening of aromatic cycles. On the other hand, oxidation in the presence of metal salts does not cause a change in pH, which suggests that the oxidation observed is a Fenton type oxidation without opening of the rings.

Claims

1. Process for the selective oxidation of organic substrates by bringing said substrates into contact with an oxidant chosen from hydroperoxides and / or hydrogen peroxide in the presence of a catalyst formed from at least one metal complex of at least one multicomponent nitrogenous ligand with at least one transition metal, operating in an aqueous and / or organic diluent, characterized in that the metal / peroxide complex molar ratio is between 1 and 10 ^"10 and the temperature is less than 120 ° C. and in that the metal complex of general formula (I) corresponding to:

[L _χ M _y X _u ] ^z Y _q (I) in which M is a metal from the group consisting of manganese and iron in at least one of the possible oxidation states II, III, IV or V,

X is a bridging species of metals chosen from the group consisting of water, hydroxide ions OH ^" , oxygen ions O ^2- , 0 ₂ ^2" and 0 ₂ ^" , sulfur ions S ^2- , peroxide ions HOO ^" , the carboxylated ions RC00 ^~ , R being a hydrogen atom, an optionally substituted alkyl or aryl group, and the sulphate, phosphate, carbonate and halide ions,

Y is a counterion of the group consisting of halides, chlorates, borates, sulfates, phosphates, nitrates, perchlorates, sulfonates, triflates and hexafluorophosphate, with x and y denoting whole numbers or equal to 1, u denoting an integer varying from 0 to 3, z an integer corresponding to the charge of the metal complex and q being equal to the ratio of z to the charge of Y, and finally, L is a ligand chosen from the ligands of formula (II) below: * ι _^ Ar ₂

~ ^ N - '(CH ₂ ) _r - N ^ (II)

A _{r ι} / R2

in which identical and different Ari ^{and Ar} 2 are constituted by a linear carbon chain containing from 1 to

6 carbon atoms linked to at least one heterocycle comprising at least one optionally protonated nitrogen atom, Ri and R ₂ being identical or different and representing groups consisting of the hydrogen atom or a linear or branched alkyl chain containing 1 to 6 carbon atoms optionally linked to at least one heterocycle comprising at least one nitrogen atom possibly protonated, and with r an integer between 2 and 4.

2. Method according to claim 1 characterized in that the organic substrates are compounds of the group consisting of linear or branched alkanes, cyclic alkanes, linear or branched alcohols and mono, di and polyaromatic compounds optionally containing a heteroatom, which are present in solution, suspension or emulsion in an oxidation inert, aqueous or semi-aqueous organic medium such as the water / acetonitrile mixture and the water / dichloromethane mixture.

3. Method according to claim 1 or 2, characterized in that the ligands of formula (II) contain from 4 to 6 nitrogen atoms capable of coordinating with the same metal by at least three of these nitrogen atoms.

4. Method according to one of claims 1 to 3 characterized in that Ari and Ar ₂ correspond in the ligand of formula (II) to one of the formulas (III), (IV) and (V) below:

! CH2): ιn:

or

N • CH

(CH2) _D - C ⁷ IV)

CH N

V or

with p denoting an integer varying from 1 to 6 and R 'and R "representing the hydrogen atom, an alkyl group comprising from 1 to 6 carbon atoms, a halogen atom or one of the nitro, methoxy and ethoxy, the heterocycle being optionally replaced by its benzopyridyl or benzimidazolyl counterpart.

5. Method according to one of claims 1 to 4 characterized in that the iron or manganese complexes are obtained from tetracoordinated ligands with at least one metal atom, such as in formula (II), Ri and R ₂ are identical or different alkyl groups comprising from 1 to 6 carbon atoms and preferably 1 to 3 carbon atoms.

6. Method according to one of claims 1 to 5 characterized in that the tetracoordinating ligands of said complexes are chosen from the group consisting of N, N'-Bis- (2-pyridylmethyl) ethane-1,2-diamine or Bispicen, N, N'- dimethyl-N, N '-Bis- (2-pyridylmethyl) ethane-1,2-diamine or Bispicen (NMe) 2 and NN' -dimethyl-N, N '-Bis- ( 1-methyl imidazol-2-yl-methyl) ethane-1,2-diamine or (1Me) Bisim (NMe) 2.

7. Method according to claim 7, characterized in that the complexes comprising tetracoordinating ligands are chosen from the complexes of the metal-ligand system of the group constituted by the Fe-Bispicen, Mn-Bispicen, Fe-Bispicen (NMe) _{2 systems} , Mn-Bispicen (NMe) ₂ , Fe-1MeBisim (NMe) ₂ , Mn-1Me-Bisim (NMe) ₂ , Fe-1MeBisim and Mn-1MeBisim, two coordinated metals which can be grouped by μ-oxo or μcarboxylato bridges.

8. Method according to one of claims 1 to 5 characterized in that the iron and manganese complexes contain pentacoordinating ligands for which in formula (II), Ri is a group consisting of a hydrogen atom or a chain linear or branched alkyl containing from 1 to 3 carbon atoms, R ₂ , Ari ^{and Ar} 2 are identical and correspond to one of the formulas (III), (IV) or (V) in which the heterocycle has optionally been replaced by its counterpart benzopyridyl or benzimidazolyl.

9. Method according to claim 8 characterized in that the complexes of pentacoordinating ligands are complexes of the metal-ligand system Fe-N, N, N '-Tris- (2-pyridylmethyl) N' - methylethane-1, 2-diamine or Fe-TrispicMeen.

10. Method according to one of claims 1 to 5 characterized in that the iron and manganese complexes contain hexacoordinating ligands of formula (II) in which RI, R2 correspond as Ari and Ar2 to one of the formulas (III ), (IV) or (V), in which the heterocycle has optionally been replaced by its benzopyridyl or benzimidazolyl counterpart.

11. The method of claim 10 characterized in that the iron and manganese complexes are the complexes of hexacoordinating ligands corresponding to metal-ligand systems of the group consisting of metal / ligand systems Fe- N, N, N ', N '-tetrakis- (2-pyridylmethyl) ethane-1,2-diamine or Fe-Tpen and Mn-N, N, N', N '-tetrakis- (2-pyridylmethyl) ethane-1,2-diamine or Mn- Tpen.

12. Method according to one of claims from 1 to 11 characterized in that the oxidation reactions take place in an inert oxidation, organic, aqueous or semi-aqueous medium, in particular the water / acetonitrile mixture or the water / dichloromethane mixture, in the presence of hydrogen peroxide or terbutylhydroperoxide, the metal complexes being present in solution or impregnated on an inert support with regard to oxidation, of the group consisting of resins, clays, silicas, active carbon and wool residues, or else linked by a covalent bond to a constituent element of the support, in particular by grafting and / or by insertion into the metal network of the support.

13. Application of the method according to one of claims 1 to 11 to the controlled oxidation of organic substrates, preferably alkanes and alcohols, this application being characterized in that the initial molar ratio of oxidant / substrate is less than 0, 5.

14. Application of the method according to one of claims 1 to 11 to the complete oxidation of organic substrates, this application being characterized in that the initial oxidant / substrate molar ratio is greater than or equal to 0.5, and preferably greater at 1.

15. Oxidation catalyst for organic substrates present in aqueous, semi-aqueous or organic solution, optionally supported by a solid inert to oxidation, containing iron and / or manganese complexes, characterized in that said metallic complex is of general formula (I) corresponding to:

[L _x M _y X _u ] ^z Y _q (I) and in which M is a metal from the group consisting of manganese and iron in at least one of the possible oxidation states II, III, IV or V, X is a bridging species of metals chosen from the group consisting of water, hydroxide ions OH ^" , oxygen ions 0 ^{2 ~} , 0 ₂ ^2" and 0 ₂ ^" , sulfur ions S ^2" , peroxide ions HOO ^" , the carboxylated ions RCOO ^" , R being an atom hydrogen, an optionally substituted alkyl or aryl group, and the sulphate, phosphate, carbonate and halide ions,

Y is a counterion of the group consisting of halides, chlorates, borates, sulfates, phosphates, nitrates, perchlorates, sulfonates, triflates and hexafluorophosphate, with x and y denoting whole numbers at 1, u denoting an integer varying from 0 to 3, z an integer corresponding to the charge of the metal complex and q is equal to the ratio of z to the charge of Y, the ratio x / y varying from 0.5 to 5 and preferably from 0.5 to 2 and finally, L is a ligand chosen from the ligands of formula (VIII) below:

RI. Ar-} /

N - (CH2) _S - N _^ (VIII)

\

Ar- / Ar-

in which s represents an integer ranging from 2 to 6, Ari, ^Ar 2 ^{and Ar} 3 ^ΞAre identical or different and consist of a linear carbon chain containing from 1 to 6 carbon atoms linked to at least one heterocycle comprising at least an optionally protonated nitrogen atom, Ri a group consisting of a hydrogen atom or a linear or branched alkyl chain containing from 1 to 6 carbon atoms optionally connected to at least one heterocycle comprising at least one optionally protonated nitrogen atom .

16. Catalyst according to claim 15 characterized in that Ari, Ar ₂ and Ar ₃ correspond to one of the formulas below:

or

R "with p denoting an integer varying from 1 and 6 and R ′ and R" corresponding to the hydrogen atom, an alkyl group comprising from 1 to 6 carbon atoms, a halogen atom, and in which we has optionally replaced the heterocycle with its counterpart benzopyridyl or benzimidazolyl

17. Oxidation catalyst according to claim 15 or 16, characterized in that each ligand of formula (VIII) coordinates with at least one metal atom from the group consisting of manganese and iron in at least one of the possible states of oxidation II, III, IV or V, by at least three of its nitrogen atoms, the first two coming from the diamine chain, the following from the nitrogen atoms present in nitrogen heterocycles.

18. Oxidation catalyst according to one of claims 15 to 17, characterized in that two metal atoms are linked by a chemical bridging of the group consisting of the ligand (s), the μ-oxo, μ-carboxylato, hydroxo bridges .

19. Oxidation catalyst according to one of claims 15 to 18, characterized in that it contains at least one complex containing a pentacoordinating ligand of formula (VIII) in which s equal to 2, Ri is a group consisting of a hydrogen atom or a linear or branched alkyl chain containing from 1 to 3 carbon atoms, Ari, Ar ₂ and Ar ₃ are identical or different and correspond to one of the formulas (III), (IV) and (V) .

20. Oxidation catalyst according to one of claims 15 to 19, characterized in that Ari, ^Ar 2 ^{and Ar} 3 are identical with formula (III) with p equal to 1.

21. Oxidation catalyst according to one of claims 15 to 20, characterized in that the complexes are chosen from metal / ligand systems from the group consisting of Fe-N, N, N '-tris- (2- pyridylmethyl) -N '-methyl-ethane-1,2-diamine or Fe-TrispicMeen and Mn-N, N, N' -tris- (2-pyridylmethyl) -N '-methyl-ethane-1,2-diamine or Mn- TrispicMeen.

22. Oxidation catalyst according to one of claims 15 to 19, characterized in that in formula (VIII), Ari, ^Ar 2 and Ar ₃ are identical with formula (IV) with p equal to 1 or 2.

23. Oxidation catalyst according to one of claims 15 to 19, characterized in that in formula (VIII), Ari, ^Ar 2 and Ar ₃ are identical with formula (V) with p equal to 1 or 2.

24. Oxidation catalyst according to one of claims 15 to 18, characterized in that the iron or manganese complexes contain at least one hexacoordmant ligand, of formula (VIII) in which Ri, Ari, ^Ar ₂ ^{and Ar} 3 are the same or different and correspond to one of the formulas (III), (IV) and (V).

25. Oxidation catalyst according to claim 24, characterized in that in the ligand of formula (VIII), s is equal to 2, Ri, Ari, ^Ar 2 ^{and Ar} 3 ^are identical with formula

(III), and p is 1 or 2.

26. Oxidation catalyst according to claim 25, characterized in that the complexes are chosen from metal / ligand systems from the group consisting of metal / ligand systems Fe-N, N, N ', N' -tetrakis- (2 -pyridylmethyl) ethane - 1,2-diamine or Fe-TPEN and Mn-N, N, N ', N' -tetrakis- (2-pyridylmethyl) ethane -1,2-diamine or Mn-TPEN.

27. Oxidation catalyst according to claim 24, characterized in that in the ligand of formula (VIII), s is equal to 2, Ri, Ari, ^Ar 2 ^{and Ar} 3 are identical with formula

(IV), and p is 1 or 2.

28. Oxidation catalyst according to claim 24, characterized in that in the ligand of formula (VIII), s is equal to 2, Ri, Ari, ^Ar 2 ^{and Ar} 3 are identical with formula

(V), and p is 1 or 2.