DE102012019441A1 - Preparing a formamide and/or formate compound comprises homogeneous-catalyst conversion of a reaction mixture comprising carbon dioxide, hydrogen and an amine compound in the presence of an iridium catalyst and a bivalent phosphine ligand - Google Patents

Abstract

Preparing formamide compound (Ia) and/or formate compound (Ib) comprises homogeneous-catalyst conversion of a reaction mixture comprising carbon dioxide, hydrogen and an amine compound (II) in the presence of an iridium catalyst, at least one bivalent phosphine ligand, in a hydrogenation reactor (I), to obtain a hydrogenation mixture containing (Ia), (Ib), iridium catalyst and/or optionally unreacted (II). Preparing formamide compound of formula (H-C(=O)-N(R1)(R2)) (Ia) and/or formate compound of formula ((H-C(=O)-O ->)(N +>H 2R1R2)) (Ib) comprises homogeneous-catalyst conversion of a reaction mixture comprising carbon dioxide, hydrogen and an amine compound of formula (NHR1R2) (II) in the presence of an iridium catalyst, at least one bivalent phosphine ligand, in a hydrogenation reactor (I), to obtain a hydrogenation mixture containing (Ia), (Ib), iridium catalyst and/or optionally unreacted (II). Either R1, R2 : 1-16C-alkyl, 5-8C-cycloalkyl, 5-8C-heterocyclyl, 5-10C-aryl, 5-10C-heteroaryl (all unsubstituted or monosubstituted by 1-10C-alkyl, 5-8C-cycloalkyl or 5-10C-aryl) or H; or R1R2N : 5-7 membered ring optionally further comprising one or more heteroatoms of O, S or N, where N contains the substituent R1b; and R1b : H or 1-6C-alkyl.

Description

The present invention relates to a process for the preparation of formamide compounds and / or formates by homogeneously catalyzed reaction of a reaction mixture containing carbon dioxide, hydrogen and an amine in the presence of an iridium catalyst.

Formamide and its N-substituted derivatives are important selective solvents and extractants because of their polarity. They are used, for example, for the extraction of butadiene from C ₄ cuts, from acetylene from C ₂ crack fractions and from aromatics from aliphatics.

All large-scale production processes for the production of formamide and its alkyl derivatives have so far used carbon monoxide as the C _{1 building} block.

Formamide, N-alkylformamide and N, N-dialkylformamide are prepared by reacting methyl formate, which is accessible by the reaction of carbon monoxide with methanol, with ammonia, N-alkylamines or N, N-dialkylamines. The liberated methanol can be recycled to the Methylformiatsynthese from carbon monoxide and methanol.

In another, also technically used synthesis, ammonia or the abovementioned amines are reacted at 20 to 100 ° C. and 2 to 10 MPa directly with carbon monoxide instead of methyl formate. Work is carried out in methanol as solvent with alkoxides as catalysts ( Hans-Jürgen Arpe, Industrial Organic Chemistry, 6th edition, 2007, pages 48 to 49 ).

Carbon monoxide is a comparatively expensive C _{1 building} block. A disadvantage of carbon monoxide is beyond its toxicity, which makes working under high safety precautions necessary. Furthermore, the relatively high pressures in the production of formamides from carbon monoxide are costly.

L. Vaska et. al., Journal of Molecular Catalysis, 52, (1989) L11 to L16 describes the reaction of carbon dioxide with hydrogen in the presence of ammonia and methanol as solvent to formamide. The homogeneous catalyst used is trans-chlorocarbonylbis (triphenylphosphine) iridium ([Ir (Cl) (CO) (Ph ₃ ) ₂ ]). The hydrogenation is carried out at a temperature of 125 ° C and a pressure of 122 atm. A disadvantage of the process described therein is that very long reaction times are necessary and only low TON values (TON, turnover number) are achieved. The TON values after a reaction time of 2 days are 594 and after a reaction time of 10 days 1145 in each case based on iridium. The synthesis of N-substituted formamide derivatives as well as the recovery of the iridium catalyst and the organic solvent are not described.

The object of the present invention is to provide a process for the homogeneously catalyzed preparation of formamide and N-substituted formamide derivatives based on the starting compounds carbon dioxide, hydrogen and an amine. The process should be able to be operated continuously. The preparation of formamide and N-substituted formamide derivatives should preferably be carried out in one reaction step (integrated process). Formamide and N-substituted formamide derivatives are to be made accessible with high yields and selectivity. The work-up of the reaction order should be technically simple, require little energy and preferably take place exclusively with substances already present in the process. In addition, a method is to be provided, with which much higher TON values can be achieved and which enables a separation and recycling of the catalyst.

in denen
R¹ und R² unabhängig voneinander Wasserstoff, unsubstituiertes oder zumindest monosubstituiertes C₁-C₁₆-Alkyl, C₅-C₈-Cycloalkyl, C₅-C₈-Heterocyclyl, C₅-C₁₀-Aryl oder C₅-C₁₀-Heteroaryl sind,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus C₁-C₁₀-Alkyl, C₅-C₆-Cycloalkyl und C₅-C₁₀-Aryl
oder
R¹ und R² zusammen mit dem Stickstoffatom, an das sie gebunden sind, einen fünf- oder sechsgliedrigen Ring bilden, der gegebenenfalls zusätzlich ein oder mehrere Heteroatome ausgewählt aus O, S und N enthält, wobei N den Substituenten R^b trägt, der Wasserstoff oder C₁-C₆-Alkyl ist;
durch homogen-katalysiertes Umsetzen eines Reaktionsgemischs (Rg), das Kohlendioxid, Wasserstoff und ein Amin der allgemeinen Formel (II) enthält HNR¹R² (II), in der R¹ und R² die vorstehenden Bedeutungen aufweisen, in einem Hydrierreaktor in Gegenwart eines Iridium-Katalysators, der einen mindestens zweizähnigen Phosphinliganden enthält, unter Erhalt eines Hydriergemischs (H), das die Formamidverbindung (Ia) und/oder das Formiat (Ib), den Iridium-Katalysator sowie gegebenenfalls nicht umgesetztes Amin (II) enthält.This object is achieved by a process for the preparation of formamide compounds of the general formula (Ia) and / or formates of the general formula (Ib)

in which
R ¹ and R ² independently of one another are hydrogen, unsubstituted or at least monosubstituted C ₁ -C ₁₆ -alkyl, C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ Heteroaryl are,
wherein the substituents are selected from the group consisting of C ₁ -C ₁₀ alkyl, C ₅ -C ₆ cycloalkyl and C ₅ -C ₁₀ aryl
or
R ¹ and R ² together with the nitrogen atom to which they are attached form a five- or six-membered ring optionally additionally containing one or more heteroatoms selected from O, S and N, wherein N bears the substituent R ^b , which is hydrogen or C ₁ -C ₆ alkyl;
by homogeneously catalyzed reaction of a reaction mixture (Rg) containing carbon dioxide, hydrogen and an amine of general formula (II) HNR ¹ R ² (II), in which R ¹ and R ^{2 have} the above meanings, in a hydrogenation reactor in the presence of an iridium catalyst containing an at least bidentate phosphine ligand to obtain a hydrogenation mixture (H) containing the formamide compound (Ia) and / or the formate (Ib ), the iridium catalyst and optionally unreacted amine (II).

The inventive method allows the use of inexpensive carbon dioxide instead of the relatively expensive carbon monoxide as C ₁ -Baustein. In addition, the process of the invention, the simple separation and recycling of the expensive catalyst, good product yields and the simple workup of the reaction order allows.

The preparation of formamide compounds (Ia) by hydrogenation of carbon dioxide in the presence of an amine (II) and an iridium catalyst can be represented by the following reaction equation 1:

The inventive reaction of carbon dioxide, hydrogen and an amine (II) is carried out at temperatures in the range of 50 to 180 ° C, preferably 70 to 150 ° C and particularly preferably in the range of 100 to 125 ° C. At lower temperatures, formates (Ib) are formed. The formation of the formates takes place according to the following reaction equation 2:

The formates (Ib) can be subsequently reacted, for example, by reactive distillation to formamide compound (Ia). The reaction follows the following reaction equation 3:

Ie. one mole of carbon dioxide, one mole of hydrogen and one mole of amine (II) form one mole of formamide compound (Ia) and one mole of water of reaction.

In the process according to the invention, a reaction mixture (Rg) is reacted which contains carbon dioxide, hydrogen and an amine (II). In a preferred embodiment, the reaction mixture (Rg) additionally contains at least one polar solvent.

In the context of the present invention, "formamide compound (Ia)" is understood as meaning both formamide (H- (C =O) -NH ₂ ) itself and N-substituted formamide derivatives. For the preparation of formamide compounds (Ia), in a preferred embodiment, the amine (II) is an amine selected from the group consisting of ammonia, methylamine, dimethylamine, ethylamine, diethylamine, n-propylamine, di-n-propylamine, isopropylamine, diisopropylamine, n-butylamine, di-n-butylamine, isobutylamine, diisobutylamine, morpholine, piperidine, piperazine and aniline used. As a result, the corresponding formamide compounds (Ia) are selected from the group consisting of formamide, methylformamide, dimethylformamide, ethylformamide, diethylformamide, n-propylformamide, di-n-propylformamide, isopropylformamide, diisopropylformamide, n-butylformamide, di-n-butylformamide, isobutylformamide, Diisobutylformamide, N-formylmorpholine, N-formylpiperidine, N-formylpiperazine and formanilide accessible.

In a further preferred embodiment, an amine selected from the group consisting of ammonia, methylamine and dimethylamine is used as amine (II). As a result, the corresponding formamide compounds (Ia) selected from the group consisting of formamide, methylformamide, dimethylformamide accessible.

In a particularly preferred embodiment, ammonia is used as the amine (II) and formamide is obtained as the formamide compound (Ia).

In a further particularly preferred embodiment, morpholine is used as amine (II) and formylmorpholine is obtained as formamide compound (Ia).

For the formates (Ib), the definitions and preferences given above for the formamide compound (Ia) apply correspondingly.

In principle, all reactors which are fundamentally suitable for homogeneously catalyzed gas / liquid reactions under the given temperature and the given pressure can be used as hydrogenation reactors. Suitable standard reactors for gas-liquid reaction systems are, for example, in KD Henkel, "Reactor Types and Their Industrial Applications," and Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH Verlag GmbH & Co. KGaA, DOI: 10.1002114356007.b04_087 described. Examples which may be mentioned stirred tank reactors, tubular reactors or tube bundle reactors.

The amines (II) used in the process according to the invention are fed to the hydrogenation reactor in liquid or gaseous form. Hydrogen and carbon dioxide can be fed to the hydrogenation reactor as separate streams. It is also possible to supply the hydrogenation reactor with a gas stream containing carbon dioxide and hydrogen. The carbon dioxide used in the reaction of carbon dioxide with hydrogen in the hydrogenation reactor can be used solid, liquid or gaseous. It is also possible to use commercially available carbon dioxide-containing gas mixtures. The hydrogen and carbon dioxide may also contain other inert gases such as nitrogen or noble gases. Advantageously, the total content of inert gases in the gas streams fed to the hydrogenation reactor is below 20 mol% based on the total amount of carbon dioxide and hydrogen in the hydrogenation reactor. While larger amounts may also be tolerable, they generally require the use of a higher pressure in the reactor, requiring further compression energy.

The molar ratio of carbon dioxide to the amine (II) used in the process of the invention in the feed of the hydrogenation reactor is generally in the range of 1 to 1 to 1 to 5, preferably in the range of 1 to 1 to 1 to 2. Particularly preferably, the molar ratio is 1 to 1.

The molar ratio of carbon dioxide to hydrogen in the feed of the hydrogenation reactor is generally in the range of 1 to 1 to 1 to 10, preferably in the range of 1 to 1 to 1 to 5 and more preferably in the range of 1 to 1 to 1 to 2. In particular the molar ratio of carbon dioxide to hydrogen in the feed of the hydrogenation reactor is 1 to 2.

The hydrogenation of carbon dioxide in the liquid phase is generally carried out at a temperature in the range of 50 to 180 ° C, preferably in the range of 70 to 150 ° C and more preferably in the range of 100 to 125 ° C.

The hydrogenation of carbon dioxide is generally carried out at a total pressure in the range of 50 to 250 bar, preferably in the range of 100 to 200 bar and particularly preferably in the range of 120 to 150 bar.

In a preferred embodiment, the hydrogenation of carbon dioxide is carried out at a temperature in the range of 100 to 125 ° C and a total pressure in the range of 120 to 150 bar.

The partial pressure of the carbon dioxide in the hydrogenation is generally in the range from 1 to 100 bar, preferably in the range from 5 to 50 bar and particularly preferably in the range from 20 to 30 bar.

The hydrogen partial pressure in the hydrogenation is generally in the range from 10 to 200 bar, preferably in the range from 30 to 150 bar and particularly preferably in the range from 50 to 100 bar.

In a preferred embodiment of the process according to the invention, the hydrogenation is carried out in the presence of at least one polar solvent. In this embodiment, the reaction mixture (Rg) contains at least one polar solvent. This is particularly advantageous when amines (II) are used, such as ammonia, which form salts with carbon dioxide. By using a polar solvent, the solubility of these salts in the reaction mixture (Rg) can be improved.

In the process of the invention, the reaction mixture (Rg) may contain a polar solvent or mixtures of two or more polar solvents. Suitable classes of substances which are suitable as polar solvents are preferably alcohols and diols and also their formic acid esters, formamides such as formamide, methylformamide or dimethylformamide, or water.

Suitable alcohols are, for example, methanol, ethanol, 2-methoxyethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol and 2-methyl-1-propanol.

Suitable classes of compounds which are suitable as polar solvents are preferably diols and also their formic acid esters, polyols and also their formic acid esters, sulfones, sulfoxides, open-chain or cyclic amides and mixtures of the mentioned classes of substances.

Suitable diols and polyols are, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, dipropylene glycol, 1,5-pentanediol, 1,6-hexanediol and glycerol.

A suitable sulfone is tetramethylene sulfone (sulfolane).

Suitable sulfoxides are, for example, dialkyl sulfoxides, preferably C ₁ - to C ₆ -dialkyl sulfoxides, in particular dimethyl sulfoxide.

Suitable open-chain or cyclic amides are, for example, formamide, methylformamide, dimethylformamide, ethylformamide, diethylformamide, n-propylformamide, di-n-propylformamide, isopropylformamide, diisopropylformamide, n-butylformamide, di-n-butylformamide, tert-butylformamide, di-tert-butylformamide. butylformamide, n-hexylformamide, di-n-hexylformamide, cyclohexylformamide, dicyclohexylformamide, formanilide, N-methylpyrrolidone, acetamide and N-methylcaprolactam.

Ie. In principle, formamide compounds (Ia) which are obtainable by the process according to the invention are also suitable as polar solvents. These can be produced in the hydrogenation itself. It is also possible to supply these from the outside of the hydrogenation reactor.

The molar ratio of the polar solvent or solvent mixture used in the process according to the invention to the amine (II) used is generally from 0.5 to 30, and preferably from 1 to 20.

The quantitative ratio of the polar solvent or solvent mixture to carbon dioxide (g used polar solvent or solvent mixture / g of carbon dioxide used) is generally in the range of 1 g to 1 g to 50 g to 1 g and preferably in the range of 1 g to 1 g to 20 g to 1 g. The amount ratio is particularly preferably 1 g to 1 g.

The iridium catalyst used in the process according to the invention is formed in situ under the reaction conditions in the hydrogenation reactor. The iridium catalyst is generally available under the reaction conditions in the hydrogenation reactor from an iridium compound and at least one bidentate phosphine ligands. Suitable iridium compounds are, for example, selected from the group consisting of iridium (III) chloride (IrCl ₃ ), iridium (III) chloride hydrate (IrCl ₃ .H ₂ O), iridium (III) chloride hydrochloride hydrate (IrCl ₃ · H ₂ O · HCl), iridium (III) bromide (IrBr ₃ ), iridium (IV) chloride hydrate (IrCl ₄ · H ₂ O), iridium (IV) oxide (IrO ₂ ), Potassium hexachloroiridate (IV) (K ₂ IrCl ₆ ), potassium pentachloronitrosyl-iridium (III) (Klr (NO) Cl ₅ ), sodium hexachloroiridate (III) hydrate (Na ₃ IrCl ₆ .H ₂ O), sodium hexachloroiridate (IV) hexahydrate (Na ₂ IrCl ₆ (H ₂ O) ₆ ), ammonium hexachloroiridate (III) monohydrate ((NH ₄ ) ₃ IrCl ₆ H ₂ O), ammonium hexachloroiridate (IV) ((NH ₄ ) ₂ IrCl ₆ ), tetrairidium dodecacarbonyl (Ir ₄ (CO) ₁₂ ), hydrogen hexachloroiridate (IV) hydrate (H ₂ Cl ₆ Ir • H ₂ O), trans -chlorocarbonylbis (triphenylphosphine) iridium ([Ir ( Cl) (CO) (Ph ₃ ) ₂ ]) Bis (1,5-cyclooctadiene) diiridium (I) dichloride ([Ir (COD) Cl] ₂ ), hydridocarbonyltris (triphenylphosphine) iridium (I) (IrH (CO) (PPh ₃ ) ₃ ), B is (triphenylphosphine) iridium (I) carbonyl chloride ([IrCl (CO) (PPh ₃ ) ₂ ]), (1,5-cyclooctadiene) (pyridine) (tricyclohexylphosphine) iridium (I) hexafluorophosphate ([Ir ( COD) (PCy ₃₎ (Py)] PF _6), (iridium III) acetylacetonate (Ir (acac) _3), tris ^{[2-phenylpyridinato-C2,} N] (iridium (III) Ir (ppy) ₃₎ , (1,5-cyclooctadiene) (hexafluoroacetylacetonato) iridium (I) (Ir (COD) (C ₅ HF ₆ O ₂ )), (1,5-cyclooctadiene) (methoxy) iridium (I) dimer ([Ir ( OMe) (COD)] ₂ ), (1,5-cyclooctadiene) -η ⁵ -indenyl) iridium (I) ((C ₉ H ₇ ) Ir (COD)), (methylcyclopentadienyl) (1,5-cyclooctadiene) iridium (I) ((C ₆ H ₇ ) Ir (COD)), (1,5-cyclooctadiene) bis (methyldiphenylphosphine) iridium (I) hexafluorophosphate ([Ir (COD) (PPh ₂ Me) ₂ ] PF ₆ ), 3-Di-isopropylphosphine-2- (N, N-dimethylamine) -1H-indene (1,5-cyclooctadiene) iridium (I) hexafluorophosphate ([IrC ₂₅ H ₃₈ NP] PF ₆ ), (acetylacetonato) (1, 5-cyclooctadiene) iridium (I) (Ir (acac) (COD)), dicarbonylacetylacetonato-iridium (I) (Ir (CO) ₂ (acac)), tris (norbornadiene) (acetylacetonato) iridium (III) (Ir (C ₇ H ₈ -C ₇ H ₈₎ (C ₇ H ₈ ) (acac)), bis (1,5-cyclooctadiene) iridium (I) tetrafluoroborate ([Ir (COD) ₂ ] BF ₄ ), bis (1,5-cyclooctadiene) iridium (I) - tetrakis (3,5-bis (trifluoromethyl) phenyl) borate ([Ir (COD) ₂ ] BARF), chlorobis (cyclooctene) iridium (I) dimer (C ₃₂ H ₅₆ Cl ₂ Ir ₂ ), chlorodihydrido [bis (2 -diisopropylphosphino) ethylamine] iridium (III) (C ₁₆ H ₃₉ ClIrNP _2), trichlorotris (pyridine) (iridium (III) (Ir Py) ₃ Cl _3), tris [1-phenylisoquinoline-C ^2, N] iridium (III ) (Ir (piq) ₃ ), tris [2- (4,6-difluorophenyl) pyridinato-C ² , N] iridium (III) (Ir (Fppy) ₃ ), tris [2- (benzo [b] thiophene) 2-yl) pyridinato-C ³ , N] iridium (III) (Ir (btpy) ₃ ), dichlorotetrakis (2- (2-pyridinyl) phenyl) diiridium (III) ([(ppy) ₂ IrCl] ₂ ), chloro (pentamethylcyclopentadienyl) [(2-pyridinyl-kN) phenyl-kC] iridum (III) (IrCl (C ₁₀ H ₁₅ ) (ppy)) and dichloro (pentamethylcyclopentadienyl) iridium (III) dimer ([(CH ₃ ) ₅ C ₅ IrCl ₂ ] ₂ ).

Particularly preferred iridium compounds are iridium complex compound. Suitable iridium complex compounds are, for example, selected from the group consisting of bis (1,5-cyclooctadiene) diiridium (I) dichloride ([Ir (COD) Cl] ₂ ), hydridocarbonyltris (triphenylphosphine) iridium (I) (IrH (CO) (PPh ₃ ) ₃ ), bis (triphenylphosphine) iridium (I) carbonyl chloride ([IrCl (CO) (PPh ₃ ) ₂ ]), (1,5-cyclooctadiene) (pyridine) (tricyclohexylphosphine) -iridium (I. ) hexafluorophosphate ([Ir (COD) (PCy ₃₎ (Py)] PF _6), iridium (III) acetylacetonate (Ir (acac) _3), tris [2-phenylpyridinato-C ^2, N] iridium (III) (Ir (ppy) ₃ ), (1,5-cyclooctadiene) (hexafluoroacetylacetonato) iridium (I) (Ir (CID) (C ₅ HF ₆ O ₂ )), (1,5-cyclooctadiene) (methoxy) iridium (I. ) -dimer ([Ir (OMe) (COD)] ₂ ), (1,5-cyclooctadiene) -η ⁵ -indenyl) iridium (I) ((C ₉ H ₇ ) Ir (COD)), (methylcyclopentadienyl) ( 1,5-cyclooctadiene) iridium (I) ((C ₆ H ₇ ) Ir (COD)), (1,5-cyclooctadiene) bis (methyldiphenylphosphine) iridium (I) hexafluorophosphate ([Ir (COD) (PPh ₂ Me ) ₂ ] PF ₆ ), 3-di-isopropylphosphine-2- (N, N-dimethylamine) -1H-indene (1,5-cyclooctadiene) iridium (I) - hexafluorophosphate ([IrC ₂₅ H ₃₈ NP] PF ₆ ), (acetylacetonato) (1,5-cyclooctadiene) iridium (I) (Ir (acac) (COD)), dicarbonylacetylacetonato-iridium (I) (Ir (CO) ₂ ( acac), tris (norbornadiene) (acetylacetonato) iridium (III) (Ir (C ₇ H ₈ -C ₇ H ₈ ) (C ₇ H ₈ ) (acac)), bis (1,5-cyclooctadiene) iridium (I. ) tetrafluoroborate ([Ir (COD) ₂ ] BF ₄ ), bis (1,5-cyclooctadiene) iridium (I) tetrakis (3,5-bis (trifluoromethyl) phenyl) borate ([Ir (COD) ₂ ] BARF ), Chlorobis (cyclooctene) iridium (I) dimer (C ₃₂ H ₅₆ C ₁₂ Ir ₂ ), chlorodihydrido [bis (2-diisopropylphosphino) ethylamine] iridium (III) (C ₁₆ H ₃₉ ClIrNP ₂ ), trichlorotris (pyridine) iridium (III) (Ir (Py) ₃ Cl ₃ ), tris [1-phenylisoquinoline-C ² , N] iridium (III) (Ir (piq) ₃ ), tris [2- (4,6-difluorophenyl) pyridinato] C ² , N] iridium (III) (Ir (Fppy) ₃ ), tris [2- (benzo [b] thiophen-2-yl) pyridinato-C ³ , N] iridium (III) (Ir (btpy) ₃ ) Dichlorotetrakis (2- (2-pyridinyl) phenyl) diiridium (III) ([(ppy) ₂ IrCl] ₂ ), chloro (pentamethylcyclopentadienyl) [(2-pyridinyl-kN) phenyl-kC] iridum (III) (IrCl ( C ₁₀ H ₁₅ ) (ppy)) and dichloro (pentamethylcyclopentadienyl) iridium (III) dimer ([(CH ₃ ) ₅ C ₅ IrCl ₂ ] ₂ ).

Most preferred are iridium complex compounds containing COD as ligands.

"COD" means 1,5-cyclooctadiene, "(PPh ₃ )" means triphenylphosphine.

In the context of the present invention, homogeneously catalyzed means that the iridium catalyst formed in the hydrogenation reactor is at least partially dissolved in the liquid reaction medium (liquid phase of the reaction mixture (Rg)). In a preferred embodiment, at least 90% of the iridium catalyst formed in the hydrogenation reactor is dissolved in the liquid reaction medium, more preferably at least 95%, most preferably more than 99%, most preferably the iridium catalyst is completely dissolved in the liquid reaction medium (100 %), in each case based on the total amount of iridium catalyst present in the liquid reaction medium.

In a further preferred embodiment, "homogeneously catalyzed" means that the iridium compound and the at least bidentate phosphine ligand are each at least partially soluble in the liquid reaction medium. In a preferred embodiment, the iridium compound and the at least bidentate phosphine ligand are at least 90% soluble in the liquid reaction medium, more preferably at least 95%, more preferably more than 99%, most preferably both the iridium compound and also the at least bidentate phosphine ligand completely soluble in the liquid reaction medium (100%), in each case based on the total amount of the iridium compound or the used at least bidentate phosphine in the liquid reaction medium (liquid phase of the reaction mixture Rg).

The amount of the metal component (iridium) of the iridium catalyst in the hydrogenation is generally from 0.1 to 5000 ppm by weight, preferably from 1 to 800 ppm by weight and more preferably from 5 to 800 ppm by weight, in particular from 50 to 250 Ppm by weight, in each case based on the liquid phase of the reaction mixture (Rg) in the hydrogenation reactor.

The molar ratio of the metal component (iridium) of the iridium catalyst to carbon dioxide in the reaction mixture (Rg) is generally in the range of 1 to 2,000 to 1 to 50,000, preferably in the range of 1 to 5,000 to 1 to 20,000.

The molar ratio of iridium to the at least bidentate phosphine ligand in the iridium catalyst is generally in the range of 1 to 1 to 1 to 5, preferably in the range of 1 to 1 to 1 to 2. In particular, the molar ratio is 1 to 1.

With the method according to the invention, TOF values of up to 5,000 are generally achieved. (TON value = mole of formamide compound (Ia) per mole of iridium in the iridium catalyst based on the reaction time; TOF value = mole of formamide compound (Ia) per mole of iridium in the iridium catalyst per 1 hour reaction time). Turnover Frequency (TOF) and Turnover Number TON; for the definition of TOF and TON see: JF Hartwig, Organotransition Metal Chemistry, 1st Edition, 2010, University Science Books, Sausalito, California p. 545 )

In the context of the present invention, denticity is understood to mean the number of bonds that the phosphine ligand can form to the iridium central atom. Ie. at least bidentate phosphine ligands can form at least two bonds to the iridium central atom.

in der
m, q unabhängig voneinander 0, 1, 2 oder 3 sind;
R³, R⁴ beide Wasserstoff sind oder gemeinsam mit den Kohlenstoffatomen, an die sie gebunden sind, einen unsubstituierten oder zumindest monosubstituierten Phenylring bilden,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OC(O)R^a, -OCOCF₃, -OSO₂R^a, -OSO₂CF₃, -CN, -OH, -OR^a, -N(R^a)₂, -NHR^a und unsubstituiertem oder zumindest monosubstituiertem C₁-C₁₀-Alkyl,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OH, -CN, -NH₂, -COOH und C₁-C₁₀-Alkyl;
R⁵ Wasserstoff, -F, -Cl, -Br, -OC(O)R^a, -OCOCF₃, -OSO₂R^a, -OSO₂CF₃, -CN, -OH, -OR^a, -N(R^a)₂, -NHR^a oder unsubstituiertes oder zumindest monosubstituiertes C₁-C₁₀-Alkyl ist,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OH, -CN, -NH₂, -COOH und C₁-C₁₀-Alkyl;
R^a ausgewählt ist aus der Gruppe bestehend aus Wasserstoff und C₁-C₁₀-Alkyl
R⁶, R⁷ beide Wasserstoff sind oder gemeinsam mit den Kohlenstoffatomen, an die sie gebunden sind, einen unsustituierten oder zumindest monosubstiuierten Phenylring bilden,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OC(O)R^a, -OCOCF₃, -OSO₂R^a, -OSO₂CF₃, -CN, -OH, -OR^a, -N(R^a)₂, -NHR^a und unsubstituiertem oder zumindest monosubstituiertem C₁-C₁₀-Alkyl,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OH, -CN, -NH₂, -COOH und C₁-C₁₀-Alkyl;
R⁸, R⁹, R¹⁰, R¹¹ unabhängig voneinander ausgewählt sind aus der Gruppe bestehend aus unsubstituiertem oder zumindest monosubstituiertem C₁-C₁₀-Alkyl, C₅-C₈-Cycloalkyl, C₅-C₈-Heterocyclyl, C₅-C₁₀-Aryl und C₅-C₁₀-Heteroaryl,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus C₁-C₄-Alkyl und -OR^a;
X -N-, -P- oder -CH- ist.In a preferred embodiment, a phosphine ligand of the general formula (III) is used as the at least bidentate phosphine ligand,

in the
m, q are independently 0, 1, 2 or 3;
R ³ , R ^{4 are} both hydrogen or together with the carbon atoms to which they are attached form an unsubstituted or at least monosubstituted phenyl ring,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OC (O) R ^a , -OCOCF ₃ , -OSO ₂ R ^a , -OSO ₂ CF ₃ , -CN, -OH, - OR ^a , -N (R ^a ) ₂ , -NHR ^a and unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, -NH ₂ , -COOH and C ₁ -C ₁₀ alkyl;
R ^{5 is} hydrogen, -F, -Cl, -Br, -OC (O) R ^a , -OCOCF ₃ , -OSO ₂ R ^a , -OSO ₂ CF ₃ , -CN, -OH, -OR ^a , -N ( R ^a ) ₂ , -NHR ^a or unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, -NH ₂ , -COOH and C ₁ -C ₁₀ alkyl;
R ^{a is} selected from the group consisting of hydrogen and C ₁ -C ₁₀ alkyl
R ⁶ , R ^{7 are} both hydrogen or together with the carbon atoms to which they are attached form an unsubstituted or at least monosubstituted phenyl ring,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OC (O) R ^a , -OCOCF ₃ , -OSO ₂ R ^a , -OSO ₂ CF ₃ , -CN, -OH, - OR ^a , -N (R ^a ) ₂ , -NHR ^a and unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, -NH ₂ , -COOH and C ₁ -C ₁₀ alkyl;
R ⁸ , R ⁹ , R ¹⁰ , R ^{11 are} independently selected from the group consisting of unsubstituted or at least monosubstituted C ₁ -C ₁₀ alkyl, C ₅ -C ₈ cycloalkyl, C ₅ -C ₈ heterocyclyl, C ₅ -C ₁₀ -aryl and C ₅ -C ₁₀ -heteroaryl,
wherein the substituents are selected from the group consisting of C ₁ -C ₄ alkyl and -OR ^a ;
X is -N-, -P- or -CH-.

Particularly preferred is a phosphine ligand of the general formula (III) in which
m, q are independently 0 or 1;
R ³ , R ^{4 are} both hydrogen or together with the carbon atoms to which they are attached form an unsubstituted phenyl ring,
R ^{5 is} hydrogen, -F, -Cl, -Br, OC (O) R ^a , -OCOCF ₃ , -OSO ₂ R ^a , -OSO ₂ CF ₃ , -CN, -OH, -OR ^a , -N (R ^a ) ₂ , -NHR ^a or unsubstituted C ₁ -C ₁₀ -alkyl,
R ^{a is} selected from the group consisting of hydrogen and C ₁ -C ₄ alkyl
R ⁶ , R ^{7 are} both hydrogen or together with the carbon atoms to which they are attached form an unsubstituted phenyl ring,
R ⁸ , R ⁹ , R ¹⁰ , R ^{11 are} independently selected from the group consisting of unsubstituted or at least monosubstituted C ₁ -C ₆ -alkyl, C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ -aryl and C ₅ -C ₁₀ -heteroaryl,
wherein the substituents are selected from the group consisting of C ₁ -C ₄ alkyl and -OCH ₃ ;
X is -N- or -CH-.

in denen für R⁵, R⁸, R⁹, R¹⁰ und R¹¹ die vorstehend zur allgemeinen Formel (III) angeführten Definitionen und Bevorzugungen entsprechend gelten.In a further preferred embodiment, the hydrogenation is carried out in the presence of an iridium catalyst which comprises a phosphine ligand (III) selected from the group of the phosphine ligands of the general formulas (IIIa), (IIIb), (IIIc), (IIId) (IIIe), Contains (IIIf), (IIIg) and (IIIh),

in which, for R ⁵ , R ⁸ , R ⁹ , R ¹⁰ and R ^11, the definitions and preferences given above for the general formula (III) apply correspondingly.

In a particularly preferred embodiment, R ⁵ in the general formulas (IIIa), (IIIb), (IIIc), (IIId) (IIIe), (IIIf), (IIIg) and (IIIh) is hydrogen and R ⁸ , R ⁹ , R ¹⁰ and R ¹¹ are independently selected from the group consisting of iso-propyl, tert-butyl, cyclohexyl, phenyl and 2-methoxyphenyl, 3-methoxyphenyl and 4-methoxyphenyl.

Particularly preferred at least bidentate phosphine ligands are those selected from the group consisting of 2,6-bis (di-tert-butylphosphinomethyl) pyridine (CAS No. 338800-13-8), 1,3-bis (di-tert-butylphosphinomethyl) benzene (CAS No. 149968-36-5), 4,5-bis (dicyclohexylphosphino) acridine and 4,5-bis (dicyclohexylphosphino) anthracene.

in der
n 0 oder 1 ist,
R²¹, R²², R²³, R24, R²⁵, R²⁶ unabhängig voneinander unsubstituiertes oder zumindest monosubstituiertes C₁-C₁₀-Alkyl, C₁-C₄-Alkyldiphenylphosphin (-C₁-C₄-Alkyl-P(Phenyl)₂), C₅-C₈-Cycloalkyl, C₅-C₈-Heterocyclyl, C₅-C₁₀-Aryl oder C₅-C₁₀-Heteroaryl sind,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OH-OR²⁷, -CN, -NH₂ und C₁-C₄-Alkyl
wobei R²⁷ ausgewählt ist aus C₁-C₄-Alkyl und C₅-C₁₀-Aryl;
A gegebenenfalls substituiertes P oder N oder unsubstituiertes oder zumindest monosubstituiertes C₁-C₆-Alkan ist,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus: C₁-C₄-Alkyl, Phenyl, -F, -Cl, -Br, -OH, -OR²⁷, -NH₂, -NHR²⁷ und N(R²⁷)₂,
wobei R²⁷ ausgewählt ist aus C₁-C₄-Alkyl und C₅-C₁₀-Aryl;
Y¹, Y², Y³ unabhängig voneinander eine Bindung, unsubstituiertes oder zumindest monosubstituiertes Methylen, Ethylen, Trimethylen, Tetramethylene, Pentamethylen oder Hexamethylen sind,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OH, -OR²⁷, -CN, -NH₂, -NHR²⁷, -N(R²⁷)₂ und C₁-C₁₀-Alkyl,
wobei R²⁷ ausgewählt ist aus C₁-C₄-Alkyl und C₅-C₁₀-Aryl.In a further preferred embodiment, a phosphine ligand of the general formula (IV) is used as the at least bidentate phosphine ligand,

in the
n is 0 or 1,
R ²¹ , R ²² , R ²³ , R 24, R ²⁵ , R ²⁶ independently of one another are unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, C ₁ -C ₄ -alkyldiphenylphosphine (C ₁ -C ₄ -alkyl-P (phenyl ) ₂ ), C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ -heteroaryl,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH-OR ²⁷ , -CN, -NH ₂ and C ₁ -C ₄ alkyl
wherein R ^{27 is} selected from C ₁ -C ₄ alkyl and C ₅ -C ₁₀ aryl;
A is optionally substituted P or N or unsubstituted or at least monosubstituted C ₁ -C ₆ alkane,
wherein the substituents are selected from the group consisting of: C ₁ -C ₄ -alkyl, phenyl, -F, -Cl, -Br, -OH, -OR ²⁷ , -NH ₂ , -NHR ²⁷ and N (R ²⁷ ) ₂ ,
wherein R ^{27 is} selected from C ₁ -C ₄ alkyl and C ₅ -C ₁₀ aryl;
Y ¹ , Y ² , Y ^{3 are} independently a bond, unsubstituted or at least monosubstituted methylene, ethylene, trimethylene, tetramethylene, pentamethylene or hexamethylene,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -OR ²⁷ , -CN, -NH ₂ , -NHR ²⁷ , -N (R ²⁷ ) ₂ and C ₁ -C ₁₀ alkyl,
wherein R ^{27 is} selected from C ₁ -C ₄ alkyl and C ₅ -C ₁₀ aryl.

A is a bridging group according to the invention. In the case where A is unsubstituted or at least monosubstituted C ₁ -C ₆ -alkane, for the case (n = 0) two hydrogen atoms of the bridging group are replaced by bonds to the adjacent substituents Y ¹ and Y ² . In this case, A is preferably unsubstituted or at least monosubstituted methylene (-CH ₂ -), ethylene (-CH ₂ CH ₂ -), trimethylene (-CH ₂ CH ₂ CH ₂ -), tetramethylene (-CH ₂ CH ₂ CH ₂ CH ₂ -), pentamethylene (-CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ -) or hexamethylene (-CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ CH ₂ -). For the case (n = 1) three hydrogen atoms of the bridging group are replaced by three bonds to the adjacent substituents Y ¹ , Y ² and Y ³ .

In the case of AP (phosphorus), for the case (n = 0), the phosphorus forms two bonds to the adjacent substituents Y ¹ and Y ² and a bond to a substituent selected from the group consisting of C ₁ -C ₄ Alkyl and phenyl. For the case (n = 1), the phosphorus forms three bonds to the adjacent substituents Y ¹ , Y ² and Y ³ .

For the case that AN is (nitrogen), the nitrogen forms two bonds to the adjacent substituents Y ¹ and Y ² for the case (n = 0) and a bond to a substituent selected from the group consisting of C ₁ -C ₄ Alkyl and phenyl. For the case (n = 1), the nitrogen forms three bonds to the adjacent substituents Y ¹ , Y ² and Y ³ .

Particularly preferred are phosphine ligands of the general formula (IV) in which
n is 0,
R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ independently of one another are unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, C ₁ -C ₄ -alkyldiphenylphosphine (C ₁ -C ₄ -alkyl-P ( Phenyl) ₂ ), C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ -heteroaryl,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -OCH ₃ , -CN, -NH ₂ and C ₁ -C ₁₀ alkyl;
A is unsubstituted or at least monosubstituted methylene, ethylene, trimethylene, tetramethylene, pentamethylene or hexamethylene, wherein the substituents are selected from the group consisting of C ₁ -C ₄ alkyl, phenyl, -F, -Cl, -Br, -OH , -OR ²⁷ , -NH ₂ , -NHR ²⁷ and N (R ²⁷ ) ₂ ,
wherein R ^{27 is} selected from C ₁ -C ₄ alkyl and C ₅ -C ₁₀ aryl;
Y ¹ , Y ² bonds are.

Further particularly preferred are phosphine ligands of the general formula (IV) in which
n is 1,
R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ independently of one another are unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, C ₁ -C ₄ -alkyldiphenylphosphine (C ₁ -C ₄ -alkyl-P ( Phenyl) ₂ ), C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ -heteroaryl,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -OCH ₃ , -CN, -NH ₂ and C ₁ -C ₁₀ alkyl;
AP is,
Y ¹ , Y ² , Y ^{3 are} independently of one another, unsubstituted or at least monosubstituted methylene, ethylene, trimethylene, tetramethylene, pentamethylene or hexamethylene,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -OR ²⁷ , -CN, -NH ₂ , -NHR ²⁷ , -N (R ²⁷ ) ₂ and C ₁ -C ₁₀ alkyl,
wherein R ^{27 is} selected from C ₁ -C ₄ alkyl and C ₅ -C ₁₀ aryl.

in der
A unsubstituiertes Methylen, Ethylen, Trimethylen, Tetramethylene, Pentamethylen oder Hexamethylen ist,
R^c C₁-C₄-Alkoxy ist,
m² 0, 1 oder 2 ist.Further particularly preferred phosphine ligands are those of the general formula (IVa)

in the
A is unsubstituted methylene, ethylene, trimethylene, tetramethylene, pentamethylene or hexamethylene,
R ^{c is} C ₁ -C ₄ -alkoxy,
m ^{2 is} 0, 1 or 2.

m ² indicates the number of substituents R ^c on the phenyl rings. The phenyl rings can carry the substituent R ^c in the 2-, 3- or 4-position. The phenyl rings are preferably substituted in the 2-position. In particular, the phenyl rings each carry only one (1) substituent R ^c , ie m ² is 1. As the substituent R ^c , methoxy (-OCH ₃ ) is most preferred, wherein A is trimethylene. Another particularly preferred A trimethylene and m ² 0.

in denen
m¹, q¹ unabhängig voneinander 0, 1, 2 oder 3 sind,
R³³, R³⁴, R³⁵, R³⁶ unabhängig voneinander unsubstituiertes oder zumindest monosubstituiertes C₁-C₁₀-Alkyl, C₅-C₈-Cycloalkyl, C₅-C₈-Heterocyclyl, C₅-C₁₀-Aryl oder C₅-C₁₀-Heteroaryl sind,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OH, -OCH₃, -CN, -NH₂ und C₁-C₁₀-Alkyl;
R³⁸, R³⁹ unabhängig voneinander ausgewählt aus der Gruppe C₁-C₁₀-Alkyl, F, Cl, Br, OH, OR³⁷, NH₁, NHR³⁷ und N(R³⁷)₂ sind,
wobei R³⁷ ausgewählt ist aus C₁-C₁₀-Alkyl und C₅-C₁₀-Aryl;
X¹, X² unabhängig voneinander -NH-, -O- oder -S- sind,
X³ eine Bindung, -(NH)-, -(NR⁴⁰)-, -O-, -S- oder -(CR⁴¹R⁴²)- sind,
R⁴⁰ unsubstituiertes oder zumindest monosubstituiertes C₁-C₁₀-Alkyl, C₅-C₈-Cycloalkyl, C₅-C₈-Heterocyclyl, C₅-C₁₀-Aryl oder C₅-C₁₀-Heteroaryl ist,
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OH, -CN, -NH₂ und -C₁-C₁₀-Alkyl;
R⁴¹, R⁴² unabhängig voneinander unsubstituiertes oder zumindest monosubstituiertes C₁-C₁₀-Alkyl, C₁-C₁₀-Alkoxy, C₅-C₈-Cycloalkyl, C₅-C₈-Cycloalkoxy, C₅-C₈-Heterocyclyl, C₅-C₁₀-Aryl, C₅-C₁₀-Aryloxy oder C₅-C₁₀-Heteroaryl sind
wobei die Substituenten ausgewählt sind aus der Gruppe bestehend aus -F, -Cl, -Br, -OH, -CN, -NH₂ und C₁-C₁₀-Alkyl;In a further preferred embodiment, a phosphine ligand of the general formula (Va) or (Vb) is used as the at least bidentate phosphine ligand,

in which
m ¹ , q ^{1 are} independently 0, 1, 2 or 3,
R ³³ , R ³⁴ , R ³⁵ , R ³⁶ independently of one another are unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ heteroaryl are,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -OCH ₃ , -CN, -NH ₂ and C ₁ -C ₁₀ alkyl;
R ³⁸ , R ^{39 are} independently selected from the group C ₁ -C ₁₀ -alkyl, F, Cl, Br, OH, OR ³⁷ , NH ₁ , NHR ³⁷ and N (R ³⁷ ) ₂ ,
wherein R ^{37 is} selected from C ₁ -C ₁₀ alkyl and C ₅ -C ₁₀ aryl;
X ¹ , X ^{2 are} independently -NH-, -O- or -S-,
X ^{3 is} a bond, - (NH) -, - (NR ⁴⁰ ) -, -O-, -S- or - (CR ⁴¹ R ⁴² ) - are,
R ^{40 is} unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ -heteroaryl,
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, -NH ₂ and -C ₁ -C ₁₀ alkyl;
R ⁴¹ , R ⁴² independently of one another are unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, C ₁ -C ₁₀ -alkoxy, C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -cycloalkoxy, C ₅ -C ₈ -heterocyclyl , C ₅ -C ₁₀ aryl, C ₅ -C ₁₀ aryloxy or C ₅ -C ₁₀ heteroaryl
wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, -NH ₂ and C ₁ -C ₁₀ alkyl;

Particularly preferred at least bidentate phosphine ligands are, for example, selected from the group consisting of 1,2-bis (diphenylphosphino) ethane (dppe), 1,2-bis (dicyclohexylphosphino) ethane, 1,2-bis (diphenylphosphino) propane (dppp), 1,2 Bis (diphenylphosphino) butane (dppb), 2,3-bis (dicyclohexylphosphino) ethane (dcpe), 4,5-bis (diphenylphosphino) -9,9-dimethylxanthene (xantphos), bis (2-diphenylphosphinoethyl) phenylphosphine and 1 , 1,1-tris (diphenylphosphinomethyl) ethane (Triphos).

More preferred are, for example, phosphine ligands selected from the group consisting of 4,5-bis (diphenylphosphino) -9,9-dimethylxanthene (xantphos), bis (2-diphenylphosphinoethyl) phenylphosphine and 1,1,1-tris (diphenylphosphinomethyl) ethane (triphos).

In the context of the present invention, "at least monosubstituted" is understood to mean that the radical or the group of radicals to which this formulation relates carries one or more, preferably 1, 2, or 3, more preferably one, substituent.

In the context of the present invention, C ₁ -C ₁₆ -alkyl is understood as meaning branched, unbranched, saturated and unsaturated groups. Preferred are saturated alkyl groups having 1 to 10 carbon atoms (C ₁ -C ₁₀ alkyl), more preferred are saturated alkyl groups having 1 to 6 carbon atoms (C ₁ -C ₆ alkyl). Particularly preferred are saturated alkyl groups having 1 to 4 carbon atoms (C ₁ -C ₄ alkyl).

Examples of saturated alkyl groups are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, amyl and hexyl.

Examples of unsaturated alkyl groups (alkenyl, alkynyl) are vinyl, allyl, butenyl, ethynyl and propynyl.

The C ₁ -C ₁₆ -alkyl group can be unsubstituted or selected with one or more substituents from the group C ₁ -C ₁₀ -alkyl, C ₁ -C ₆ -alkoxy, C ₅ -C ₈ -cycloalkyl, C ₅ -C ₁₀ - Aryl substituted.

C ₅ -C ₈ -cycloalkyl is understood here to mean saturated, unsaturated monocyclic and polycyclic five- to eight-membered ring systems. Examples of C ₅ -C ₈ -cycloalkyl are cyclopentyl, cyclohexyl or cycloheptyl. The cycloalkyl groups may be unsubstituted or substituted with one or more substituents as defined above for the C ₁ -C ₁₆ alkyl group.

In the context of the present invention, C ₅ -C ₁₀ -aryl means an aromatic ring system having 5 to 10 carbons. The aromatic ring system may be monocyclic or bicyclic. Examples of aryl groups are phenyl, naphthyl, such as 1-naphthyl and 2-naphthyl. The aryl group may be unsubstituted or substituted with one or more substituents as defined above under C ₁ -C ₁₆ alkyl.

In the context of the present invention, C ₅ -C ₁₀ heteroaryl is understood as meaning a heteroaromatic system which contains at least one heteroatom selected from the group consisting of N, O and S. The heteroaryl groups may be monocyclic or bicyclic. In the case where nitrogen is a ring atom, the present invention also includes N-oxides of the nitrogen-containing heteroaryls. Examples of heteroaryls are thienyl, benzothienyl, 1-naphthothienyl, thianthrenyl, furyl, benzofuryl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, indolyl, isoindolyl, indazolyl, purinyl, isoquinolinyl, quinolinyl, acridinyl, naphthyridinyl, quinoxalinyl, Quinazolinyl, cinnolinyl, piperidinyl, carbolinyl, thiazolyl, oxazolyl, isothiazolyl, isoxazolyl. The heteroaryl groups may be unsubstituted or substituted with one or more substituents defined above under C ₁ -C ₁₆ alkyl.

In the context of the present invention, C ₅ -C ₈ -heterocyclyl is understood as meaning five- to eight-membered ring systems which contain at least one heteroatom selected from the group consisting of N, O and S. The ring systems can be monocyclic or bicyclic. Examples of suitable heterocyclic ring systems are piperidinyl, pyrrolidinyl, pyrrolinyl, pyrazolinyl, pyrazolidinyl, morpholinyl, thiomorpholinyl, pyranyl, thiopyranyl, piperazinyl, indolinyl, dihydrofuranyl, tetrahydrofuranyl, dihydrothiophenyl, tetrahydrothiophenyl, dihydropyranyl and tetrahydropyranyl.

In the context of the present invention, C ₁ -C ₆ -alkoxy refers to (C ₁ -C ₆ -alkyl-O-) radicals. Examples of the alkyl moiety of the alkoxy group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, amyl and hexyl.

The hydrogenation of carbon dioxide can be carried out batchwise or continuously in the process according to the invention. In the batchwise mode of operation of the hydrogenation reactor is equipped with the desired liquid and optionally solid feedstocks and auxiliaries and then pressed carbon dioxide and hydrogen to the desired pressure at the desired temperature. After the end of the reaction, the reactor is usually depressurized.

In the continuous mode, the feeds and auxiliaries, including the carbon dioxide and hydrogen, are continuously fed to the hydrogenation reactor. In a continuous procedure, a liquid phase is continuously removed from the hydrogenation reactor, so that the liquid level in the reactor remains the same on average. Preference is given to the continuous hydrogenation of carbon dioxide.

The average residence time of the reaction mixture (Rg) in the hydrogenation reactor is generally 10 minutes to 5 hours, preferably the residence time is 20 minutes to 1 hour.

Regardless of whether the hydrogenation is carried out continuously or batchwise, in the reaction of the reaction mixture (Rg) in the hydrogenation reactor, a hydrogenation mixture (H) is obtained which contains the formamide compound (Ia) and / or the formate (Ib), the iridium catalyst and optionally unreacted amine (II). The hydrogenation mixture (H) may additionally contain the polar solvent or solvent mixture.

Depending on the temperature, formamide compounds (Ia) and / or formates (Ib) may form in the hydrogenation. In one embodiment, substantially formamide compounds (Ia) are formed in the hydrogenation, so that the hydrogenation mixture (H) additionally contains water of reaction. In a further embodiment formamide compounds (Ia) and formates (Ib) are formed in the hydrogenation. At low temperatures, essentially formates (Ib) can also be formed in the hydrogenation. In this case, the hydrogenation mixture (H) contains no water of reaction.

In the event that a hydrogenation mixture (H) is obtained in the hydrogenation, which contains formate (Ib), they are in the further work-up, which preferably takes place by distillation, to the corresponding Formamide compound (Ia) is reacted to obtain a bottom mixture containing the iridium catalyst dissolved in the formamide compound (Ia), and is recycled to the hydrogenation reactor. The invention therefore also relates to a process in which, during the work-up by distillation, a bottom mixture is obtained which contains the iridium catalyst dissolved in formamide and is recycled to the hydrogenation reactor.

The hydrogenation mixture (H) may optionally contain gaseous components such as carbon dioxide, hydrogen, ammonia or alkylamines. The hydrogenation mixture (H) is generally depressurized before the further workup and the gaseous constituents which may be present in the hydrogenation mixture (H) are separated off and recycled to the hydrogenation reactor.

In a preferred embodiment, the hydrogenation mixture (H) is expanded in a first distillation apparatus. Optionally in the hydrogenation mixture (H) contained gaseous components such as carbon dioxide, hydrogen, ammonia or alkylamines are separated overhead of the first distillation apparatus and recycled to the hydrogenation reactor. The first distillation apparatus can be configured as a distillation column, falling film evaporator or as a flash container

In this embodiment, a worked-up hydrogenation mixture (Ha) is obtained in the first distillation apparatus, which is largely free of gaseous components and the formamide compound (Ia) and / or formate (Ib) and optionally water of reaction and optionally contains the polar solvent or solvent mixture. The worked-up hydrogenation mixture (Ha) may optionally contain unreacted amine (II). The composition of the worked-up hydrogenation mixture (Ha) depends on the composition of the hydrogenation mixture (H) obtained in the hydrogenation. In the event that a polar solvent or solvent mixture was used in the hydrogenation, this is contained in the worked-up hydrogenation mixture (Ha). The reclaimed hydrogenation mixture (Ha) can then be subsequently fed to a second distillation apparatus. The work-up by distillation can be one, two or more stages depending on the separation problem.

In the second distillation apparatus, reaction water, the polar solvent optionally contained and the unreacted amine (II) which may be present are separated off from the worked-up hydrogenation mixture (Ha). In the preparation of formamide compounds (Ia) in the presence of a polar solvent, distillation in the second distillation apparatus can be carried out with separation of low-boiling polar solvents such as the monohydric alcohols methanol, ethanol, propanols and butanols under normal pressure or in vacuo. In a preferred embodiment, the polar solvents are recycled to the hydrogenation reactor. In contrast, when using higher-boiling polar solvents, such as diols, the distillative workup at reduced pressure, preferably in the range of 0.1 to 500 mbar abs. prefers. Unreacted amine (II) is separated in a preferred embodiment in the distillation in the second distillation apparatus and recycled to the hydrogenation reactor. Likewise, we recycled an optional polar solvent in a preferred embodiment after distillation to the hydrogenation reactor. The separated reaction water is discarded. It is also possible to carry out the separation of the water of reaction only in the third distillation apparatus.

Depending on the separation problem, different apparatus can be used as distillation units for the second distillation apparatus. At far apart boiling points of the substances involved, formamide compound (Ia), unreacted amine (II) and optionally polar solvent, z. B. evaporators such as falling film evaporator can be used. However, the second distillation apparatus generally comprises a distillation column containing packing, packing and / or trays.

When using an additional polar solvent, the second distillation apparatus comprises at least one, preferably two to three, distillation columns. These columns contain, depending on the separation problems z. B. packing, packages and / or floors.

It is also possible to feed the hydrogenation mixture (H) directly to the second distillation apparatus. In this embodiment, the separation of the gaseous components takes place in the second distillation apparatus.

In the second distillation apparatus, a sump mixture (S1) containing the formamide compound (Ia) and / or the formate (Ib) and the iridium catalyst is generally obtained.

The bottoms mixture (S1) is subsequently fed to a third distillation apparatus. In the case where the bottom mixture (S1) contains formate (Ib), this becomes complete in the third distillation device or partially converted to the corresponding formamide compound (Ia). The resulting water of reaction is discharged from the third distillation apparatus and discarded. The third distillation apparatus is preferably designed as a distillation column. From the third distillation apparatus, the target product, the formamide compound (Ia), discharged. The resulting formamide compounds (Ia) have purities in the range of 99 to 99.9%.

In the bottom of the third distillation apparatus, a bottom mixture (S2) is obtained which contains the iridium catalyst, the formamide compound (Ia) and optionally the formate (Ib). The iridium catalyst is preferably dissolved in the formamide compound (Ia). The bottoms mixture (S2) is discharged from the third distillation apparatus and recycled in a preferred embodiment to the hydrogenation reactor. As a result, an effective separation of the expensive iridium catalyst from the target product, the formamide compound (Ia), and its return to the hydrogenation is possible. The recycled iridium catalyst shows substantially no decrease in TOF values.

In a further embodiment, the hydrogenation mixture (H) is expanded and the resulting worked-up hydrogenation mixture (Ha) is then fed directly to the third distillation apparatus. This embodiment is particularly advantageous if the hydrogenation is carried out without the addition of a polar solvent. Further, this embodiment is advantageous when the hydrogenation is carried out in the presence of high-boiling polar solvents. In this case, the sump mixture (S2) additionally contains the high-boiling polar solvent and optionally excess at least bidentate phosphine ligands.

The invention will be explained with reference to the following figure, without limiting it thereto.

1 shows a block diagram of a preferred embodiment of the process according to the invention for the preparation of formamide. In 1 the reference signs have the following meanings.

LIST OF REFERENCE NUMBERS

I

hydrogenation reactor

 II

second distillation device

III

third distillation device

 1

Stream containing carbon dioxide

2

Stream containing hydrogen

3

Stream containing ammonia

 4a

Stream containing methanol

 4b

Stream containing methanol

5

Stream containing ammonium formate, formamide, methanol, water of reaction and the iridium catalyst (hydrogenation mixture worked up (Ha))

6

Stream containing ammonium formate, formamide, water of reaction and the iridium catalyst (bottoms mixture (S1))

7

Stream containing water of reaction

8th

Stream containing the target product formamide

 9

Stream containing the iridium catalyst dissolved in formamide and optionally excess at least bidentate phosphine ligands (bottom mixture (S2))

In the embodiment according to 1 be carbon dioxide, electricity 1 , Hydrogen, electricity 2 , and the ammonia, electricity 3 into the hydrogenation reactor I guided. Optionally, via a stream 4a Methanol be fed to compensate for any losses of methanol. In the hydrogenation reactor I the reaction of carbon dioxide with hydrogen and ammonia takes place in the presence of the iridium catalyst, with formamide (Ia) and / or ammonium formate (Ib) and water of reaction forming (hydrogenation mixture (H)). From the hydrogenation mixture (H) optionally contained gaseous components are separated and the hydrogenation reactor I returned (not shown). The resulting worked-up hydrogenation mixture (Ha) containing formamide (Ia) and / or ammonium formate (Ib), water of reaction and the iridium catalyst is used as stream 5 the second distillation apparatus II fed. In this, the reclaimed hydrogenation mixture (Ha) is worked up by distillation, being separated overhead methanol, which as a stream 4b to the hydrogenation reactor I is returned. In the second distillation apparatus, a bottoms mixture (S1) is obtained, which contains formamide (Ia) and / or ammonium formate (Ib), water of reaction and the iridium catalyst, and as stream 6 the third distillation apparatus III is supplied. In this ammonium formate (Ib) is partially or completely converted to formamide (Ia). The water of reaction is at the top of the third distillation apparatus III as electricity 7 discharged. The target product, formamide (Ia) is called electricity 8th taken. In the bottom of the third distillation apparatus III a sump mixture (S2) is obtained which contains the iridium catalyst dissolved in formamide and optionally excess at least bidentate phosphine ligands. The sump mixture (S2) is called electricity 9 recycled to the hydrogenation reactor.

The invention will be explained below with reference to exemplary embodiments without being limited thereto.

1 hydrogenation

1.1 Experiment description

The experiments were carried out in a 250 ml Hastelloy autoclave (hydrogenation reactor) equipped with a magnetic stirrer bar under inert gas (nitrogen). The autoclave was charged with a solution of the iridium compound and the at least bidentate phosphine ligand in methanol. Subsequently, carbon dioxide, ammonia and hydrogen were pressed at room temperature. While stirring (700 rpm), the reaction mixture (Rg) was heated to the desired temperature.

After the intended reaction time, the autoclave was cooled and expanded to remove gaseous components. The worked-up hydrogenation mixture (Ha) was weighed. Solid was filtered off and also weighed.

The composition of the liquid reaction product (worked up hydrogenation mixture (Ha)) was determined by gas chromatography (GC). Otherwise, the content of formamide and ammonium formate was determined by ¹ H NMR spectroscopy with chloroform as the internal standard. From the result of the ¹ H-NMR analysis, the TON (mole of formamide (FAM) per mole of (Ir) iridium), the TOF values (mole of formamide per mole of iridium and hour) and the reaction rate (mole of formamide per kg of worked up Hydrogenation mixture (Ha) and hour). Per mole of formamide is formed according to the reaction equation 1 (see description) one mole of water. Therefore, the amount of water formed was determined by Karl Fischer titration (KF value).

1.2 Comparative Example 1

In the L. Vaska et. al., Journal of Molecular Catalysis, 52 (1989), L11 to 16 described one-step preparation of formamide by hydrogenation of carbon dioxide in the presence of ammonia and trans-Chlorcarbonylbis- (triphenylphosphine) iridium was followed. The results in Table 1 confirm that under the given conditions only low TOF values of 146 and low reaction rates of only 0.06 are achieved. In addition, it has been found that considerable amounts of ammonium carbamate are formed, which can consume the starting materials carbon dioxide and ammonia and block parts of the hydrogenation apparatus.

1.3 Inventive Example 1

By contrast, Example 1 according to the invention demonstrates that, when using an iridium catalyst which is obtainable from ir [(cyclooctadiene) Cl] ₂ as the iridium compound and 2,6-bis (di-tert-butylphosphinomethyl) pyridine as the phosphine ligand, among the Conditions of Comparative Example 1 significantly higher TOF values (936) and reaction rates (0.44 mol of formamide per kg reaction output and hour) can be achieved. The formation of ammonium carbamate is not observed. Table 1 reaction Inventive Example 1 Comparative Example 1 Iridium catalyst 0.013 g of [Ir (COD) Cl] ₂ 0.015 g of 2,6-bis (di-tert-butylphosphinomethyl) pyridine 0.026 g IrCl (CO) (PPh ₃ ) ₂ Polar solvent 50.0 g of methanol 50.0 g of methanol Amine (II) k 9.9 g NH ₃ 9.3 g NH ₃ Pressing on C0 ₂ With 22.7 g to 1.6 MPa abs With 22.6 g to 1.6 MPa abs Pressing H ₂ At 9.4 MPa abs At 9.4 MPa abs reaction conditions Heat At 125 ° C At 125 ° C pressure change At 14.3 MPa abs At 12.5 MPa abs reaction time 5 hours 5 hours Hydrogenation mixture (H) Liquid phase (GC) 75.5 g 5.1% water 83.5% methanol 11.4% formamide 27.2 g 1.2% water 97.3% methanol 1.5% formamide Solid ammonium carbamate 0 g 10.5 g KF 3.1% water 1.6% water ¹ H-NMR (CHCl ₃ as internal standard) 119% formamide 4.2% ammonium formate 29% formamide 3.3% ammonium formate TON MOI _FAM / mole _Ir 4678 730 TOF mol _FAM / mol _Ir / h 936 h ^-1 146 h ^-1 reaction rate 0.44 mol kg ^-1 h ^-1 0.06 mol kg ^-1 h ^-1

2 recycling of the iridium catalyst in the hydrogenation

2.1 Inventive Example 2a

Example 2a in Table 2 was carried out analogously to Example 1 according to the invention. TOF values of 538 and reaction rates of 0.46 mol of formamide per kg of liquid reaction output and hour were obtained. The worked up hydrogenation mixture (Ha) (78 g) was distilled. Methanol was distilled off at normal pressure. The distillation bottoms (bottoms mixture (S1)) were then distilled at 125 ° C bottom temperature and 3 Torr pressure. The distillate contained 84% formamide by GC analysis. The bottom product (bottom mixture (S2)) (1.1 g) contained the iridium catalyst dissolved in formamide.

2.2 Inventive example 2b

The 1.1 g of bottom product (bottom mixture (S2)) from Example 2a were used as catalyst in Example 2b. Example 2b was carried out as Example 2a. TOF values of 467 and reaction rates of 0.40 mol of formamide per kg of liquid reaction output and hour were achieved. After distillation, a bottom product (bottom mixture (S2) (1.8 g) containing the iridium catalyst was obtained.

2.3 Inventive Example 2c

The bottom product (bottoms mixture (S2) (1.8 g) from Example 2b in Example 2c was used analogously to Example 2b to obtain TOF values of 498 and reaction rates of 0.43 mol of formamide per kg of liquid reaction output and hour.

Examples 2a to 2c show that the iridium catalyst can be separated off in the bottom product of the distillative workup and recycled to the hydrogenation without significant decrease in the TOF values and reaction rates. Table 2 reaction Inventive Example 2a Inventive example 2b Inventive Example 2c Iridium Katalysatorr 0.022 g of [Ir (COD) Cl) ₂ 0.025 g of 2,6-bis (di-tert-butylphosphinomethyl) pyridine 1.1 g of Sumpfgemisch (S2) (Recycling B-2a) 1.8 g swamp mixture (S2) f (recycling B-2b) Polar solvent 50.0 g of methanol 50.0 g of methanol 50.0 g of methanol Amine (II) 9.9 g NH ₃ 9.2 g NH ₃ 8.7 g of NH ₃ Pressing on CO ₂ With 22.4 g to 3.2 MPa abs With 22.4 g to 1.9 MPa abs With 22.7 g to 1.8 MPa abs Pressing H ₂ To 11.1 MPa abs At 9.7 MPa abs To 9.6 MPa abs reaction conditions Heat At 125 ° C At 125 ° C At 125 ° C pressure change At 13.7 MPa abs At 13.5 MPa abs At 13.6 MPa abs reaction time 5 hours 5 hours 5 hours Hydrogenation mixture (H) Liquid phase (GC) 78.0 g 5.6% water 82.7% methanol 11.7% formamide 77.9 g 5.1% water 84.5% methanol 10.4% formamide 76.7 g 4.8% water 84.0% methanol 11.2% formamide solid fuel 0 g 0 g 0 g KF 4.5% water 4.0% water 3.8% water ¹ NMR (CHCl ₃ as 12.7% formamide 11.1% formamide 13.2% formamide internal standard) 5.5% ammonium formate 4.9% ammonium formate 5.8% ammonium formate TON mol _FAM / mol _Ir 2689 2336 2490 TOF MOl _FAM / mol _Ir / h 538 h ^-1 467 h ^-1 498 h ^-1 reaction rate 0.46 mol kg ^-1 h ^-1 0.40 mol kg ^-1 h ^-1 0.43 mol kg ^-1 h ^-1 Distillate (GC) 8.9 g 3.2% water 3.5% NH ₃ 9.3% formic acid 84.0% formamide 7.0 g 2.4% water 3.3% NH ₃ 14.5% formic acid 79.9% formamide No distillation Swamp mixture (S2) 1.1 g of catalyst in formamide 1.8 g of catalyst in formamide

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• Hans-Jürgen Arpe, Industrial Organic Chemistry, 6th edition, 2007, pages 48 to 49 [0005]
• L. Vaska et. al., Journal of Molecular Catalysis, 52, (1989) L11 to L16 [0007]
• KD Henkel, "Reactor Types and Their Industrial Applications," and Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH Verlag GmbH & Co. KGaA, DOI: 10.1002114356007.b04_087 [0021]
• JF Hartwig, Organotransition Metal Chemistry, 1st Edition, 2010, University Science Books, Sausalito, California, p. 545 [0050]
• L. Vaska et. al., Journal of Molecular Catalysis, 52 (1989), L11 to 16 [0102]

Claims (13)

Process for the preparation of formamide compounds of general formula (Ia) and / or formates of general formula (Ib),

in which R ¹ , R ^2, independently of one another, are hydrogen, unsubstituted or at least monosubstituted C ₁ -C ₁₆ -alkyl, C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ - C _{10 are} heteroaryl, the substituents being selected from the group consisting of C ₁ -C ₁₀ -alkyl, C ₅ -C ₈ -cycloalkyl and C ₅ -C ₁₀ -aryl or R ¹ and R ² together with the nitrogen atom, to which they are attached form a five- or six-membered ring optionally additionally containing one or more heteroatoms selected from O, S and N, wherein N bears the substituent R ^b , which is hydrogen or C ₁ -C ₆ -alkyl; by homogeneously catalyzed reaction of a reaction mixture (Rg) containing carbon dioxide, hydrogen and an amine of general formula (II), HNR ¹ R ² (II) in which R ¹ and R ^{2 have} the above meanings, in a hydrogenation reactor in the presence of an iridium catalyst containing an at least bidentate phosphine ligand to obtain a hydrogenation mixture (H) containing the formamide compound (Ia) and / or the formate (Ib ), the iridium catalyst and optionally unreacted amine (II). A process as claimed in claim 1, wherein the at least bidentate phosphine ligand used is a phosphine ligand of the general formula (III),

where m, q are independently 0, 1, 2 or 3; R ³ , R ^{4 are} both hydrogen or together with the carbon atoms to which they are attached form an unsubstituted or at least monosubstituted phenyl ring, the substituents being selected from the group consisting of -F, -Cl, -Br, -OC ( O) R ^a , -OCOCF ₃ , -OSO ₂ R ^a , -OSO ₂ CF ₃ , -CN, -OH, -OR ^a , N (R ^a ) ₂ , -NHR ^a and unsubstituted or at least monosubstituted C ₁ -C ₁₀ alkyl, wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, -NH ₂ , -COOH and C ₁ -C ₁₀ alkyl; R ^{5 is} hydrogen, -F, -Cl, -Br, -OC (O) R ^a , -OCOCF ₃ , -OSO ₂ R _a , -OSO ₂ CF ₃ , -CN, -OH, -OR ^a , -N ( R ^a ) is ₂ , -NHR ^a or unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, where the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, -NH ₂ , -COOH and C ₁ -C ₁₀ -alkyl; R ^{a is} selected from the group consisting of hydrogen and C ₁ -C ₁₀ alkyl R ⁶ , R ^{7 are} both hydrogen or together with the carbon atoms to which they are attached form an unsubstituted or at least monosubstituted phenyl ring, the substituents selected are from the group consisting of -F, -Cl, -Br, -OC (O) R ^a , -OCOCF ₃ , -OSO ₂ R ^a , -OSO ₂ CF ₃ , -CN, -OH, -OR ^a , - N (R ^a ) ₂ , -NHR ^a and unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, where the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, -NH ₂ , -COOH and C ₁ -C ₁₀ -alkyl; R ⁸ , R ⁹ , R ¹⁰ , R ^{11 are} independently selected from the group consisting of unsubstituted or at least monosubstituted C ₁ -C ₁₀ alkyl, C ₅ -C ₈ cycloalkyl, C ₅ -C ₈ heterocyclyl, C ₅ C ₁₀ aryl and C ₅ -C ₁₀ heteroaryl, wherein the substituents are selected from the group consisting of C ₁ -C ₄ alkyl and -OR ^a ; X is -N-, -P- or -CH-. A process according to claim 2, wherein a phosphine ligand of the general formula (III) is used, in which m, q are independently 0 or 1; R ³ , R ^{4 are} both hydrogen or together with the carbon atoms to which they are attached form an unsubstituted phenyl ring, R ^{5 is} hydrogen, -F, -Cl, -Br, -OC (O) R ^a , -OCOCF ₃ , -OSO ₂ R ^a , -OSO ₂ CF ₃ , -CN, -OH, -OR ^a , -N (R ^a ) ₂ , -NHR ^a or unsubstituted C ₁ -C ₁₀ -alkyl, R ^{a is} selected from the group consisting of hydrogen and C ₁ -C ₄ alkyl R ⁶ , R ^{7 are} both hydrogen or together with the carbon atoms to which they are attached, form an unsubstituted phenyl ring, R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ independently are selected from the group consisting of unsubstituted or at least monosubstituted C ₁ -C ₆ alkyl, C ₅ -C ₈ cycloalkyl, heterocyclyl, C ₅ -C ₁₀ aryl and C ₅ -C ₁₀ heteroaryl, wherein the substituents selected are selected from the group consisting of C ₁ -C ₄ alkyl and -OCH ₃ ; X is -N- or -CH-. A process according to claim 2 or 3, wherein a phosphine ligand selected from the group of the phosphine ligands of the general formulas (IIIa), (IIIb), (IIIc), (IIId) (IIIe), (IIIf), (IIIg) and (IIIh) is used becomes,

in which, for R ⁵ , R ⁸ , R ⁹ , R ¹⁰ and R ^11, the definitions and preferences given above for the general formula (III) apply correspondingly. Process according to any one of claims 2 to 4, wherein R ^{5 is} hydrogen. A process according to claim 1, wherein the at least bidentate phosphine ligand used is a phosphine ligand of the general formula (IV)

in which n is 0 or 1, R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ independently of one another are unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, C ₁ -C ₄ -alkyldiphenylphosphine (-C ₁ C ₄ -C ₈ alkyl-P (phenyl) ₂ ), C ₅ -C ₈ cycloalkyl, C ₅ -C ₈ heterocyclyl, C ₅ -C ₁₀ aryl or C ₅ -C ₁₀ heteroaryl, wherein the substituents are selected are selected from the group consisting of -F, -Cl, -Br, -OH-OR ²⁷ , -CN, -NH ₂ and C ₁ -C ₄ alkyl, wherein R ^{27 is} selected from C ₁ -C ₄ alkyl and C ₅ -C ₁₀ aryl; A is optionally substituted P or N or unsubstituted or at least monosubstituted C ₁ -C ₆ alkane, where the substituents are selected from the group consisting of C ₁ -C ₄ -alkyl, phenyl, -F, -Cl, -Br, - OH, -OR ²⁷ , -NH ₂ , -NHR ²⁷ and N (R ²⁷ ) ₂ , wherein R ^{27 is} selected from C ₁ -C ₄ alkyl and C ₅ -C ₁₀ aryl; Y ¹ , Y ² , Y ³ independently of one another are a bond, unsubstituted or at least monosubstituted methylene, ethylene, trimethylene, tetramethylene, pentamethylene or hexamethylene, where the substituents are selected from the group consisting of -F, -Cl, -Br, - OH, -OR ²⁷ , -CN, -NH ₂ , -NHR ²⁷ , -N (R ²⁷ ) ₂ and C ₁ -C ₁₀ -alkyl, where R ^{27 is} selected from C ₁ -C ₄ -alkyl and C ₅ - C ₁₀ aryl. A process according to claim 6, wherein a phosphine ligand of the general formula (IV) is used in which n is 0, R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ independently of one another unsubstituted or at least monosubstituted C ₁ -C _10- alkyl, C ₁ -C ₄ -alkyldiphenylphosphine (C ₁ -C ₄ -alkyl-P (phenyl) ₂ ), C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ - Aryl or C ₅ -C ₁₀ heteroaryl, wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -OCH ₃ , -CN, -NH ₂ and C ₁ -C ₁₀ alkyl; A is unsubstituted or at least monosubstituted methylene, ethylene, trimethylene, tetramethylene, pentamethylene or hexamethylene, wherein the substituents are selected from the group consisting of C ₁ -C ₄ alkyl, phenyl, -F, -Cl, -Br, -OH , -OR ²⁷ , -NH ₂ , -NHR ²⁷ and N (R ²⁷ ) ₂ , wherein R ^{27 is} selected from C ₁ -C ₄ alkyl and C ₅ -C ₁₀ aryl; Y ¹ , Y ² bonds are. A process according to claim 6, wherein a phosphine ligand of the general formula (IV) is used in which n is 1, R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ independently of one another are unsubstituted or at least monosubstituted C ₁ - C ₁₀ alkyl, C ₁ -C ₄ alkyldiphenylphosphine (C ₁ -C ₄ alkyl-P (phenyl) ₂ ), C ₅ -C ₈ cycloalkyl, C ₅ -C ₈ heterocyclyl, C ₅ -C ₁₀ -Aryl or C ₅ -C ₁₀ heteroaryl, wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -OCH ₃ , -CN, -NH ₂ and C ₁ -C ₁₀ alkyl; AP is, Y ¹ , Y ² , Y ^{3 are} independently of one another, unsubstituted or at least monosubstituted methylene, ethylene, trimethylene, tetramethylene, pentamethylene or hexamethylene, where the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -OR ²⁷ , -CN, -NH ₂ , -NHR ²⁷ , -N (R ²⁷ ) ₂ and C ₁ -C ₁₀ -alkyl, wherein R ^{27 is} selected from C ₁ -C ₄ -alkyl and C ₅ -C ₁₀ aryl. A process according to claim 1, wherein the at least bidentate phosphine ligand used is a phosphine ligand of the general formula (Va) or (Vb),

in which m ¹ , q ^{1 are} independently 0, 1, 2 or 3, R ³³ , R ³⁴ , R ³⁵ , R ³⁶ are each independently unsubstituted or at least monosubstituted C ₁ -C ₁₀ alkyl, C ₅ -C ₈ cycloalkyl , C ₅ -C ₈ heterocyclyl, C ₅ -C ₁₀ aryl or C ₅ -C ₁₀ heteroaryl, wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -OCH ₃ , -CN, -NH ₂ and C ₁ -C ₁₀ alkyl; R ³⁸ , R ^{39 are} independently selected from the group C ₁ -C ₁₀ alkyl, F, Cl, Br, OH, OR ³⁷ , NH ₂ , NHR ³⁷ and N (R ³⁷ ) ₂ , wherein R ^{37 is} selected from C ₁ -C ₁₀ alkyl and C ₅ -C ₁₀ aryl; X ¹ , X ^{2 are} independently -NH-, -O- or -S-, X ^{3 is} a bond, - (NH) -, (NR ⁴⁰ ) -, -O-, -S- or - (CR ⁴¹ R ⁴² ) - R ^{40 is} unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -heterocyclyl, C ₅ -C ₁₀ -aryl or C ₅ -C ₁₀ - Heteroaryl, wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, -NH ₂ and -C ₁ -C ₁₀ alkyl; R ⁴¹ , R ⁴² independently of one another are unsubstituted or at least monosubstituted C ₁ -C ₁₀ -alkyl, C ₁ -C ₁₀ -alkoxy, C ₅ -C ₈ -cycloalkyl, C ₅ -C ₈ -cycloalkoxy, C ₅ -C ₈ -heterocyclyl , C ₅ -C ₁₀ aryl, C ₅ -C ₁₀ aryloxy or C5-C ₁₀ heteroaryl wherein the substituents are selected from the group consisting of -F, -Cl, -Br, -OH, -CN, - NH ₂ and C ₁ -C ₁₀ alkyl. A process according to any one of claims 1 to 9, wherein the hydrogenation mixture (H) comprises a formamide compound (Ia) and a formate (Ib). A process according to claim 10, wherein the hydrogenation mixture (H) is worked up by distillation and the formate (Ib) contained in the hydrogenation mixture (H) is converted to the formamide compound (Ia). A process according to claim 11, wherein the distillative workup gives a bottom mixture containing the iridium catalyst dissolved in formamide and recycled to the hydrogenation reactor. A method according to any one of claims 1 to 12, wherein as amine (II) an amine selected from the group consisting of ammonia, methylamine, dimethylamine, ethylamine, diethylamine, n-propylamine, di-n-propylamine, isopropylamine, diisopropylamine, n-butylamine , Di-n-butylamine, isobutylamine, diisobutylamine, morpholine, piperidine, piperazine and aniline.

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