WO2017158469A1 - Methods of making alpha, beta-unsaturated carboxylic acids or salts - Google Patents

Abstract

Methods of making an α,β-unsaturated carboxylic acid or a salt thereof is disclosed. The method can include reacting an alkene and carbon dioxide with a composition comprising a metal containing carboxylation catalyst and a coordinating ligand under conditions suitable to produce the α,β-unsaturated carboxylic acid or salt thereof. The coordinating ligand can include at least two coordinating atoms selected from nitrogen (N), oxygen (O), sulfur (S), and carbene that coordinate with the metal in the carboxylation catalyst.

Description

METHODS OF MAKING ALPHA, BETA-UNSATURATED CARBOXYLIC ACIDS

OR SALTS

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of priority of U.S. Provisional Patent Application No. 62/308,504 filed March 15, 2016, and U.S. Provisional Patent Application No. 62/467,354 filed March 6, 2017. The entire contents of each of the above-referenced disclosures are specifically incorporated herein by reference without disclaimer.

BACKGROUND OF THE INVENTION

A. Field of the Invention

[0002] The invention generally concerns methods of making α,β-unsaturated carboxylic acids or salts thereof by catalytic carboxylation of alkenes with carbon dioxide. The method includes the use of a metal carboxylation catalyst and a coordinating ligand having at least two coordinating atoms selected from nitrogen (N), oxygen (O), sulfur (S), and a carbene that can coordinate with a catalytic metal in the carboxylation catalyst. B. Description of Related Art

[0003] α,β-Unsaturated carboxylic acids (e.g., acrylic acid or methacrylic acid) or salts thereof are commercially produced through a two-step oxidation of propylene process (shown below):

This process requires two reactors and two separate catalysts to oxidize the propylene to acrylic acid, which can be capital intensive and inefficient.

[0004] Various attempts have been tried to produce acrylic acid from ethylene and carbon dioxide through activation of the carbon dioxide through coordination with a transition metal center. In many of these reactions, a metallocycle shown below can be produced (See, for example Yin, et al. Coordination Chemistry Review , 1999, Vol 181, page 27-59):

where M is Ni and Ln is a phosphorous containing coordinating ligand. This metallocycle can then be degraded with strong base to form the corresponding α,β- unsaturated carboxylic acid:

[0005] Decomposition of the metallocycle has proven challenging (e.g., formation of side products, and polymeric material), and various attempts have been made to improve the overall reaction by either eliminating the formation of or facilitating the decomposition of the metallocycle. By way of example, U.S. Patent Nos. 8,697,909 and 8,652,803 to Limbach et al. each describe a process of preparing an alkali metal or alkaline earth metal salt of an α,β- ethylenically carboxylic acid by reacting a transition metal-alkene complex with carbon dioxide to produce a metallocycle. The metallocycle is then further reacted with an alkali metal or alkaline earth metal base to give an alkali metal or alkaline earth metal salt adduct of the α,β-ethylenically carboxylic acid. This metal salt adduct is then reacted with an alkene to release the alkali metal or alkaline earth metal salt adduct of the α,β-ethylenically carboxylic acid and regenerate the transition metal-alkene complex. [0006] In another example, International Application Publication No. WO 2015/132031 to Schaffner et al. describes a process for the preparation of a, β-unsaturated carboxylic acids or salts thereof, by reacting C2-C3 olefins with carbon dioxide in the presence of a transition metal catalyst complexed with phosphine ligands that use the phosphorus atoms as the coordinating atoms. This reaction takes place in the presence of a moderate-strong base having a pKa value of 7.5 to 12.5 and a halide salt. In yet another example, Manzini et al. (European Journal of Organic Chemistry, 2015, pp. 7122-7130) describes using different sodium bases with nickel-phosphine catalysts to directly produce sodium acrylate from ethylene and carbon dioxide.

[0007] While there have been many attempts to produce α,β-unsaturated carboxylic acids from alkenes and carbon dioxide, these attempts primarily use phosphine containing ligands as coordinating ligands for the transition metal catalyst. Such coordinating ligands are susceptible to degradation when exposed to oxygen. Further, these ligands are not readily separated from the metal catalyst during the reaction. Additionally, these processes are not commercially scalable in that they have inefficient conversion and selectivity rates. SUMMARY OF THE INVENTION

[0008] A discovery has been made that provides a solution to some of the problems discussed above. The solution is premised on metal coordinating ligands having non- phosphine coordinating atoms that can be used in the metal catalyzed carboxylation of alkenes and carbon dioxide reaction. In particular, the coordinating ligands of the present invention have at least two or more coordination atoms selected from nitrogen (N), oxygen (O), sulfur (S), and a carbene that coordinate with a metal of a carboxylation catalyst. In some preferred instances, at least of the two coordinating atoms can be nitrogen. Without wishing to be bound by theory, it is believed that the coordinating ligands of the present invention are more efficient when compared with phosphine ligands that use phosphorous atoms as coordinating atoms. The coordinating ligands of the present invention provide an electronic environment for the metal carboxylation catalyst, which enhances the activity and reactivity of the resulting catalyst. In particular, the ligands of the present invention are more easily separated from the metal catalyst during the reaction, which can increase conversion rates for olefins and carbon dioxide and ultimately increase selectivity rates for α,β- unsaturated carboxylic acids or salts thereof such as acrylic acid or acrylate.

[0009] In a particular aspect of the invention, a method of making an α,β-unsaturated carboxylic acid or a salt thereof is described. The method can include reacting an alkene and carbon dioxide with a metal containing carboxylation catalyst and a coordinating ligand under conditions suitable to produce the α,β-unsaturated carboxylic acid or salt thereof. The coordinating ligand can include at least two coordinating atoms selected from nitrogen (N), oxygen (O), sulfur (S), and a carbene that coordinate with a metal in the carboxylation catalyst. In some instances, the ligands of the present invention can include a phosphorous atom(s) in a non-coordinating position(s). In other preferred aspects, the ligands of the present invention do not include any phosphorous atoms. The two coordinating atoms can be the same or different. In a particular instance, the two coordinating atoms are both nitrogen and the ligand can have a general structure of:

where R₁, R₂, R₃ and R₄ are each independently a hydrogen, an alkyl, a branched alkyl, a cycloalkyl, an aryl, a substituted aryl, a heteroatom, a substituted heteroatom, a halogen, a heterocyclic, or a heteroaryl group. In other instances, R₁ and R₂, R₂ and R_3; and/or R₃ and R₄ can come together with other atoms to form a cycloalkyl, cycloalkenyl, aryl, heteroaryl, or heterocyclic ring. R₁ and R₄ can each independently be an alkyl, a branched alkyl, a cycloalkyl, an aryl, or a substituted aryl group. R₂ and R₃ can come together with other atoms to form a cycloalkyl, cycloalkenyl, aryl, heteroaryl, or heterocyclic ring. R₁ and R₂ can come together to form a heteroaryl or heterocyclic ring, and R₃ and R₄ are each independently a hydrogen, an alkyl, a branched alkyl, a cycloalkyl, an aryl, a substituted aryl, a heteroaryl group or come together to with other atoms to form a heteroaryl or heterocyclic ring. In one instance, the coordinating ligand can have the general structure of:

where R₅, R₆, R₇, R₈, R₉, R₁₀, R₁₁, R₁₂, R₁₃, and R₁₄ are independently H, alkyl, branched alkyl, aryl, substituted aryl, or substituted heteroatom (e.g., OR, SR, NR) groups. The alkyl or branched alkyl groups can have a carbon number from 1 to 10, preferably 1 to 5, more preferably 1 to 3. R₅, R_9; R₁₀, and R₁₄ can each independently be methyl (CH₃) or isopropyl ((CH₃)₂CH) groups, or combinations thereof, and R₆, R₇, R₈, Rn, R12, and R₁₃ can be hydrogen. In particular aspects, the coordinating ligand can have any one of the following specific structures:

[0010] In other instances, the coordinating ligand can have the following structure:

where R₃ and R₄ are defined above. In yet another instance, the coordinating ligand can have any one of the following specific structures:

[0011] In still other instances, the coordinating ligand can include at least two, three, four, five, or more coordinating atoms. The coordinating atoms can be different or the same. For example, the ligand can include at least two different coordinating atoms (e.g., (O, S), (N, S), (N, O), (N, carbene), (O, carbene), (S, carbene). In other aspects, the ligand can include at least two of the same coordinating atoms (e.g., (N, N), (O, O), (S, S), or (carbene, carbene). Non-limiting examples of additional coordinating ligands of the present invention include those described throughout the specification (e.g., detailed description and claims), which are incorporated into this paragraph by reference.

[0012] In addition to the metal catalysts and ligands of the present invention, a Lewis acid, an organic base (e.g., an amine), a reducing agent, an inorganic base (e.g., a hydroxide, a carbonate, a bicarbonate, or an amino salt of a Columns 1 or 2 metal), or any combination thereof can be included in a reaction composition. The Lewis acid can be a salt of a metal from Columns 1 or 2 of the Periodic Table. The reducing agent can be metal or metal salt (e.g., zinc dust), or a reducible organic compound (e.g., hydroquinone or aminophenol). The metal of the carboxylation catalyst can include at least one transition metal (e.g., a metal from Columns 4-10 of the Periodic Table), preferably, nickel (Ni) or palladium (Pd). The metal carboxylation catalyst can be homogenous solutions (e.g., single phase solutions) where the components (e.g., metal catalysts and ligands) are solubilized therein. In a particular instance, the metal carboxylation catalyst is bis(cycloocta-l,5-diene)nickel and the coordination ligand reacts with the carboxylation catalyst to form a (cycloocta-1,5- diene)nickel— coordination ligand complex. This complex can be formed in situ or formed in a separate reaction prior to adding the alkene and the carbon dioxide. The carboxylic acid or salt thereof can be reacted with an acylating agent to form a carboxylic acid derivative. In some instances the alkene can be ethylene, propylene, or styrene, and the carboxylic acid can be acrylic acid, methacrylic acid, or cinnamic acid, or salts thereof, respectively. [0013] The following includes definitions of various terms and phrases used throughout this specification.

[0014] An "aliphatic group" is an acyclic or cyclic, saturated or unsaturated carbon group, excluding aromatic compounds. An aliphatic group can include 1 to 50, 2 to 25, or 3 to 10 carbon atoms. A linear aliphatic group does not include tertiary or quaternary carbons. A branched aliphatic group includes at least one tertiary and/or quaternary carbon. A cyclic aliphatic group is includes at least one ring in its structure. Polycyclic aliphatic groups may include fused, e.g., decalin, and/or spiro, e.g., spiro[5.5]undecane, polycyclic groups. Non- limiting examples of linear, branched or cyclic, aliphatic group substituents include alkyl, halogen (e.g., fluoride, chloride, bromide, iodide), haloalkyl, haloalkoxy hydroxyl (— OH), alkyoxy (—OR'), ether (R'-O-R'), carboxylic acid (RC0₂H), ester (RC0₂OR), amine (NH or NR), ammonium (N(R')₃ ⁺, NH(R')₂ ⁺, NH₂(R')₁ ⁺, NH₃ ⁺), amide, nitro, nitrile (CN), acyl (RCO), thiol (— SH), sulfoxides, sulfonates,, phosphine (— PRR"), phosphonium (P(R)4⁺, PH(R')₃ ⁺, PH₂(R')₂ ⁺, PH₃(R')₁ ⁺, PH₄ ⁺), thioether (— S— ), where R and R" is each independently an alkyl group or haloalkyl group. [0015] An "alkyl group" is a linear or branched, substituted or unsubstituted, saturated hydrocarbon. In the context of this invention, an alkyl group has 1 to 50, 2 to 30, 3 to 25, or 4 to 20 carbon atoms. When alkyl groups disclosed in this application, the term includes all isomers and all substitution types unless otherwise stated. For example, butyl includes n- butyl, isobutyl, and tert-butyl; pentyl includes n-pentyl, 1 -methylbutyl, 2-methylbutyl, 3- methylbutyl, 1-ethylpropyl, and neopentyl. Non-limiting examples of alkyl group substituents include halogen, hydroxyl, alkyoxy, haloalkyl, haloalkoxy, carboxylic acid, ester, amine, amide, nitrile, acyl, thiol and thioether. [0016] An "alkene" or "alkenyl" is a linear or branched, unsubstituted or substituted, unsaturated hydrocarbon. In the context of this invention, an alkenyl group has 1 to 50, 2 to 30, 3 to 25, 4 to 20, 2 to 8, or 2 to 4 carbon atoms. When alkyl groups disclosed in this application, the term includes all isomers and all substitution types unless otherwise stated. Non-limiting examples of an alkene group substituents include alkyl, halogen, hydroxyl, alkyoxy, haloalkyl, haloalkoxy, carboxylic acid, ester, amine, amide, nitrile, acyl, thiol and thioether. Non-limiting examples of alkenes are shown in Structure XXXVIII and include ethylene, propene, butylene, and styrene.

[0017] An "alkynyl" group refers to a linear or branched monovalent hydrocarbon radical of at least 2 carbon atoms with at least one triple bond. In the context of this invention, the alkenyl group has 1 to 50, 2 to 30, 3 to 25, 4 to 20, or 2 to 4 carbon atoms. The alkynyl radical may be optionally substituted independently with one or more substituents described herein. Non-limiting examples include ethynyl (-C≡CH), propynyl (propargyl, -CH₂C≡CH), -C≡C-CH₃, and the like.

[0018] An "alkylene" group refers to a saturated divalent hydrocarbon group derived from a straight or branched chain saturated hydrocarbon by the removal of two hydrogen atoms. In the context of this invention, an alkenyl group has 1 to 50, 2 to 30, 3 to 25, 4 to 20 or 1 to 4 carbon atoms. Non-limiting examples of alkylene groups include methylene (-CH₂- ), ethylene (-CH₂CH₂-), isopropylene (-CH(CH₃)CH₂-), and the like.

[0019] An "aryl group" or an "aromatic group" is a substituted or unsubstituted, mono- or polycyclic hydrocarbon with alternating single and double bonds within each ring structure. Non-limiting examples of aryl group substituents include alkyl, halogen, hydroxyl, alkyoxy, haloalkyl, haloalkoxy, carboxylic acid, ester, amine, amide, nitrile, acyl, thiol and thioether.

[0020] A "heteroatom" refers to unsubstituted or substituted atom that is not carbon unless otherwise specified. Non-limiting examples of heteroatoms are oxygen (O), nitrogen (N), phosphorous (P), or sulfur (S). Non-limiting examples of heteroatoms substituents include hydrogen, aliphatic, alkyl, alkynyl, and alkenyl. [0021] A "heteroaryl group" or "hetero-aromatic group" is a mono-or polycyclic hydrocarbon with alternating single and double bonds within each ring structure, and at least one atom (heteroatom) within at least one ring is not carbon. Non-limiting examples of heteroaryl group substituents include alkyl, halogen, hydroxyl, alkyoxy, haloalkyl, haloalkoxy, carboxylic acid, ester, amine, amide, nitrile, acyl, thiol and thioether.

[0022] The "heterocyclic" group is a mono-or polycyclic saturated or unsaturated hydrocarbon with at least one atom (heteroatom) within at least one ring is not carbon. Examples of heterocyclic rings include, but are not limited to, pyrrolidinyl, tetrahydrofuranyl, dihydrofuranyl, tetrahydrothienyl, tetrahydropyranyl, dihydropyranyl, tetrahydrothiopyranyl, piperidino, morpholino, thiomorpholino, thioxanyl, piperazinyl, homo-piperazinyl, azetidinyl, oxetanyl, thietanyl, homopiperidinyl, oxepanyl, thiepanyl, oxazepinyl, diazepinyl, thiazepinyl, 2-pyrrolinyl, 3-pyrrolinyl, indolinyl, 2H-pyranyl, 4H-pyranyl, dioxanyl, 1,3- dioxolanyl, pyrazolinyl, dithianyl, dithiolanyl, dihydropyranyl, dihydrothienyl, dihydrofuranyl, pyrazolidinylimidazolinyl, imidazolidinyl, 1,2,3,4-tetrahydro iso-quinolinyl. Some non-limiting examples of a heterocyclic group wherein 2 ring carbon atoms are substituted with oxo (=0) moieties are pyrimidindionyl and 1, 1-dioxo-thiomorpholinyl.

[0023] A "haloalkyl" or "haloalkoxy" refers to an alkyl or alkoxy substituted with one or more halogen atoms.

[0024] The terms "catecholate" or "catecholate ligand" refer to ligands that include a phenyl ring. In non-limiting example, two oxygen atoms or nitrogen atoms connected to the phenyl ring at the ring' s 1 and 2 positions. The ligand connects to the metal center of the

, where R'" and R"" are each independently alkyl, aryl, or form a fused ring with the phenyl ring.

[0025] The terms "about" or "approximately" are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment, the terms are defined to be within 10%, preferably within 5%, more preferably within 1%, and most preferably within 0.5%.

[0026] The terms "wt.%", "vol.%", or "mol.%" refers to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or total moles of a material, that includes the component. In a non-limiting example, 10 grams of component in 100 grams of the material is 10 wt.% of component.

[0027] The term "substantially" and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%. [0028] The terms "inhibiting" or "reducing" or "preventing" or "avoiding" or any variation of these terms, when used in the claims and/or the specification includes any measurable decrease or complete inhibition to achieve a desired result.

[0029] The term "effective," as that term is used in the specification and/or claims, means adequate to accomplish a desired, expected, or intended result. [0030] The use of the words "a" or "an" when used in conjunction with any of the terms "comprising," "including," "containing," or "having" in the claims, or the specification, may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one."

[0031] The words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0032] The methods of the present invention can "comprise," "consist essentially of," or "consist of particular ingredients, components, compositions, etc. disclosed throughout the specification. With respect to the transitional phase "consisting essentially of," in one non- limiting aspect, a basic and novel characteristic of the methods of the present invention are their abilities to produce α,β-unsaturated carboxylic acids or salts thereof from alkenes and carbon dioxide, with the disclosed metal coordinating ligands having non-phosphine coordinating atoms.

[0033] Other objects, features and advantages of the present invention will become apparent from the following figures, detailed description, and examples. It should be understood, however, that the figures, detailed description, and examples, while indicating specific embodiments of the invention, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0035] FIG. 1 is a schematic of a method of the present invention to produce α,β- unsaturated carboxylic acids or salts thereof.

[0036] FIG. 2 shows various esters that can be made from acrylic acid.

[0037] FIG. 3 is an energy diagram of the energy values depicting reaction pathways and associated transitions states for the coupling of an alkene with CO₂ to produce α,β- unsaturated carboxylic acids or salts thereof based on the calculated values listed in Tables 3 and 4.

[0038] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and may herein be described in detail. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0039] The currently available processes to make α,β-unsaturated carboxylic acids or salts thereof use complex steps and/or phosphine ligands, which are susceptible to degradation when exposed to oxygen. In addition catalysts with phosphine coordinating ligands are not readily separated from the product phase. A discovery has been made that provides a solution to some or all of these problems. The solution is premised on the discovery of alternative metal coordinating ligands that can be used in the metal catalyzed carboxylation of alkenes and carbon dioxide reaction. In particular, the coordinating ligands of the present invention have at least two or more coordination atoms selected from nitrogen (N), oxygen (O), sulfur (S), and a carbene that coordinate with a metal of a carboxylation catalyst. [0040] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections with reference to the Figures. A. Materials

[0041] Materials used in the making of α,β-unsaturated carboxylic acids or salts include coordinating ligands of the present invention, metal carboxylation catalyst, carbon dioxide, alkenes, bases, Lewis acids and reducing agents. As described in the Methods and in the Examples some of the compounds are optional.

1. Coordinating Ligands

[0042] The coordinating ligand may be polydentate, for example, a bidentate ligand. The bidentate ligand coordinates once to the metal center of the metal carboxylation catalyst. The coordination ligand can include 2, 3, 4, 5, 6 or more coordination atoms or carbenes. The coordinating atoms can be different or the same. Non-limiting examples of combinations of at least two different coordinating atoms are (O, S), (N, S), (N, O), (N, carbene), (O, carbene), or (S, carbene). In other aspects, the ligand includes at least two of the same coordinating atoms (e.g., (N, N), (O, O), (S, S), or (carbene, carbene). In some instances, the bidentate ligand can include two or more heteroatoms (e.g., N, O, and S) or a heteroatom and a carbene (C:) that together coordinate with the metal in the metal carboxylation catalyst. The ligand can be acyclic or cyclic. In some embodiments, the coordinating ligand can include a phosphorous atom in a non-coordinating position of the ligand. In other embodiments, the coordination ligand does not include a phosphorous atom. An amount of coordinating ligand used with the metal coordination catalyst can be determined by the number of coordinating atoms. In a non-limiting example, a 1 : 1 molar ratio of coordinating ligand to metal carboxylation catalyst can be used for a bidentate ligand. a. (N,N) Ligands

[0043] In one aspect, the coordinating ligand can include two nitrogen atoms (N,N). Non-limiting examples of ligands that include nitrogen atoms include di-, tri- and polyamines, imines, diimines, pyridine, substituted pyridines, bipyridines, imidazoles, substituted imidazoles, pyrroles, substituted pyrroles, pyrazoles and substituted pyrazoles, or combinations thereof. These compounds can be used together (e.g., two pyridines in one ligand or a diimine) to form a ligand having 2 nitrogen compounds. In a preferred aspect, a bidentate ligand can have a 1,4-diaza- 1,3 -butadiene structure:

where R₁, R₂, R₃, and R₄ can each independently be a hydrogen, an alkyl, a branched alkyl, a cycloalkyl, an aryl, a substituted aryl, a substituted heteroatom, a halogen, a heterocyclic or a heteroaryl group, or where R₁ and R₂, R₂ and R_3, and/or R₃ and R₄ come together with other atoms to form a cycloalkyl, cycloalkenyl, aryl, heteroaryl, or heterocycle ring. R₁ and R₄ can each independently an alkyl, a branched alkyl, a cycloalkyl, an aryl, or a substituted aryl group. R₂ and R₃ can come together with other atoms to form a cycloalkyl, cycloalkenyl, aryl, heteroaryl, or heterocycle ring. R₁ and R₂ can come together to form a heteroaryl or heterocycle ring in combination with R₃; and R₄ can be a hydrogen, an alkyl, a branched alkyl, a cycloalkyl, an aryl, a substituted aryl, a heteroaryl group or coming together to with other atoms to form a heteroaryl or heterocyclic ring. R₁ through R₄ can include from 1 to 50 carbon atoms. Non-limiting examples of R₁ through R₄ groups include hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, octadecyl, octacosyl, nonacosyl, triacontyl, cyclohexyl, cyclopentyl, cycloheptyl, cyclooctyl, cyclodecyl, phenyl, 3-methylphenyl, 4-methylphenyl, 2,6-dimethylphenyl, 2,4,6- trimethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2,6-diethylphenyl, 2,4,6-triethylphenyl, 3- propylphenyl, 4-propylphenyl, 2,6-dipropylphenyl, 3-isopropylphenyl, 4-isopropylphenyl, 2,6-diisopropylphenyl, 2,4,6-tri-isopropylphenyl, 3-butylphenyl, 4-butylphenyl, 2,6- dibutylphenyl, 2,4,6-tributylphenyl, 3-pentylphenyl, 4-pentylphenyl, 2,6-dipentylphenyl, 2,4,6-tripentylphenyl, 3-hexylphenyl, 4-hexylphenyl, 2,6-dihexylphenyl, 2,4,6- trihexylphenyl, 3-heptylphenyl, 4-heptylphenyl, 2,6-diheptylphenyl, 2,4,6-triheptylphenyl, 3- octylphenyl, 4-octylphenyl, 2,6-dioctylphenyl, 2,4,6-trioctylphenyl, 3-nonylphenyl, 4- nonylphenyl, 2,6-dinonylphenyl, 2,4,6-trinonylphenyl, 3-decylphenyl, 4-decylphenyl, 2,6- didecylphenyl, 2,4,6-tridecylphenyl, 3-undecylphenyl, 4-undecylphenyl, 2,6- diundecylphenyl, 2,4,6-triundecylphenyl, 3-dodecylphenyl, 4-dodecylphenyl, 2,6- didodecylphenyl, 2,4,6-tridodecylphenyl and all isomers of propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl. In one instance, the R₁ and R₄ are substituted phenyl groups and R₂ and R₃ are defined as above. Such a coordinating ligand can have the general structure of:

where R₅, R₆, R₇, R₈, R₉, R₁₀, R11, R12, R13, and R14 are independently H, alkyl, branched alkyl, aryl, substituted aryl, or substituted heteroatom groups. The alkyl or branched alkyl groups can have a carbon number from 1 to 10, preferably 1 to 5, more preferably 1 to 3. In some instances, R₅, R₆, R₇, R₈, R₉, R₁₀, R11, R12, R13, and R₁₄ can be selected from methyl, ethyl, and all isomers of propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl. R₅, R₉, R₁₀, and R₁₄ can each independently be methyl (CH₃) or isopropyl ((CH₃)₂CH) groups, or combinations thereof. In particular aspects, the R₂ and R₃ are methyl or phenyl, and the coordinating ligand can have the following specific structures with their corresponding names:

l,4-bis{2,5-di(methyl)phenyl}-2-(methyl)-3-(methyl)-l,4-diazabuta-l,3-diene;

l,4-bis{2,5-di(isopropyl)phenyl}-2-(methyl)-3-(methyl)-l,4-diazabuta-l,3-diene;

l,4-bis{2,3,54ri(methyl)phenyl}-2-(methyl)-3-(methyl)-l,4-diazabuta-l,3-diene;

( 1E,2E)-N,N', 1 ,2-tetraphenyl- 1 ,2-ethanediimine.

[0044] Non-limiting examples of R₁ and R₂ joined together with other atoms includes cyclic or aromatic rings that include 4 to 10 atoms, or 5 to 6 atoms (e.g., carbon, oxygen, or sulfur). In a particular instance, R₁ and R₂ can form a pyridine ring (Structure VII) where R₃ and R₄ are as defined above. In some embodiments, R₃ and R₄ form a pyridine or substituted pyridine ring.

[0045] Suitable coordinating ligands can have the following specific structures with their corresponding names:

N-cyclohexyl- 1 -(2- { 5-m ethyl }pyridinyl)ethanimine.

N-cyclohexyl- l-(2-pyridinyl)ethanimine.

N-(2,5-diisopropyl)phenyl-l-(2-pyridinyl)ethanimine.

N-(2,5-diisopropyl)phenyl-l-(3-methyl-2-pyridinyl)ethanimine.

(E)-N-mesityl- 1 -(2-pyridinyl)methanimine

[0046] In a particular instance, R₁ and R₂ and R₃ and R₄ can form a bi-pyridyl (e.g., 2,2'- bipyridyl, (Structure VIII)), or substituted bipyridyl type structures. In a particular instance, R₁, R₂, R₃, and R₄ can join together with other carbon atoms to form phenanthroline (e.g., Structure IX) or substituted phenanthroline type structures.

[0047] Other suitable (N,N) ligands can include an amine and an imine connected through a carbon bridge as depicted in the general structure (XIII).

where R₁, R₂, R₃, and R₄ area defined as above and R₁₅ and R₁₆ can each independently be a hydrogen, an alkyl, a branched alkyl, a cycloalkyl, an aryl, a substituted aryl, a heteroatom (e.g., O), a substituted heteroatom (e.g., OR), a halogen, a heterocyclic, or a heteroaryl group, or R₄ and R₁₅ together with other atoms can form a heterocyclic or heteroaryl ring, or R₄ and R₁₆ together with other atoms can form a heterocyclic or heteroaryl ring, or R₁₆ is a chemical bond and R₃ and R₂ come together with other atoms to form a cyclic or heterocyclic ring. R₁₅ and R₁₆ can have 1 to 50 atoms (e.g., carbon atoms, or a mixture of carbon atoms and heteroatoms), 2 to 20 atoms or 3 to atoms. By way of example, the bidentate nitrogen ligand can have the following structures:

where R₃, R₄, R15, and R₁₆ are as defined above, and R₁₇, R₁₈, R19, and R₂₀ can each independently be H, alkyl, or branched alkyl groups, or R₁₇ and R₁₈, R₁₈ and R₁₉, or R₁₉ and R₂o can come together with other atoms to form cyclic, aryl, heterocyclic, heteroaryl rings, or R₁₇, R₁₈, R₁₉, and/or R₂₀ come together with other atoms can form a fused cyclic, aryl, heterocyclic, or heteroaryl ring system, or R₁₆ is a chemical bond and R₃ and R₁₇ come together with other atoms to form a cyclic or heterocyclic ring. The alkyl or branched alkyl groups can have a carbon number from 1 to 10, preferably 1 to 5, more preferably 1 to 3. In some instances, R₁₆ is a chemical bond and R₃ and R₁₇ come together to form a substituted quinoline ring system as shown in structure (XV).

where R₄, R₁₅, R₁₈, R19, and R₂₀ are as previously defined. Other suitable ligands include pyrazole or substituted pyrazole compounds as shown in structure (XVI).

where R₂i, R₂₂, R23, R24, R25, R26, R27, and R₂₈ can each independently be H, alkyl, aryl, or branched alkyl groups, or R₂i and R₂₂, R₂₁ and R₂₃, and/or R₂₃ and R₂₄ can come together with other atoms to form cyclic, aryl, heterocyclic, heteroaryl rings, or R₂₁, R₂₂, R23, and/or R₂₄ can come together with other atoms to form a fused ring system. In some instances, R₂₃ can be an electron pair, when R₂₄ is part of an aromatic ring. The alkyl or branched alkyl groups can have a carbon number from 1 to 10, preferably 1 to 5, more preferably 1 to 3.

[0048] Other suitable (N,N) bidentate ligands can have the following generic structure:

where R₄₀, R₄₁, R₄₂, R₄₃, R₄₄, and R₄₅ can be each independently H, alkyl, or branched alkyl groups or R₄₀ and R₄₁, R₄₁ and R₄₂, R₄₂ and R₄₂, R₄₃ and R₄₄, or R₄₄ and R₄₅ can come together with other atoms to form cyclic, aryl, heterocyclic, heteroaryl rings, or R₄₀, R₄₁, R₄₂, R₄₃, R₄₄, and/or R₄₅ can come together with other atoms to form a fused ring system. The alkyl or branched alkyl groups can have a carbon number from 1 to 10, preferably 1 to 5, more preferably 1 to 3. b. (N, O) and (N, S) Ligands

[0049] In other instances, the coordinating atoms can be different. For example, the ligand includes at least two different coordinating atoms (e.g., (O, S), (N, S), (N, O), (N, carbene), (O, carbene), (S, carbene). By way of example, a (Ν,Ο) or (N,S) bidentate ligand can have the following generic structure:

where R₁, R₂, R₃, R₁₅, and R₁₇ are as previously defined for structure (XIII) and X is oxygen or sulfur. Non-limiting examples of coordinating ligands having these structures are:

where R₁₇, R₁s, R₁9, R20, R21, R22, R23, R25, R26, and R₂₇ are as previously defined and R₂₅, R26, and R₂₇ can be H, alkyl, aryl, or branched alkyl groups. It should be understood that while not shown as substituted, the ring structures in (XXI) can be substituted as defined for structures (XIX). In some instances, the (N, O) ligand (XXII), where R₁ is a hydrogen and R₂ is 2, 4, 6-trimethylbenzene having the structure of:

(O, S), (O, O) and (S,S) Ligands

Suitable (O, S), (O, O) and (S,S) bidentate ligand can have the following generic

where Y is oxygen or sulfur, X is oxygen or sulfur, R₅₀ and R₅₅ can each independently be a hydrogen, an alkyl, a branched alkyl, a cycloalkyl, an aryl, a substituted aryl, a halogen, a heterocyclic, a heteroaryl group, or an electron pair, R₅₁, R₅₂, R₅₃, and R54 can each independently be a hydrogen, an alkyl, a branched alkyl, a cycloalkyl, an aryl, a substituted aryl, a heteroatom (e.g., O), a substituted heteroatom (e.g., OR), a halogen, a heterocyclic, or a heteroaryl group, or R₅₀ and R₅₁ together with other atoms can form a heterocyclic or heteroaryl ring, or R51 and R53 together with other atoms can form a heterocyclic or heteroaryl ring, or R51 is chemical bond or are each independently chemical bonds and R50 and R₅₁ come together with other atoms to form a heterocyclic ring, or R₅₄ is a chemical bond and R54 through R₅₅ come together with other atoms to form a heterocyclic ring. R₅₀, R₅₁, R52, R₅₃, R54, and R55 can have 1 to 50 atoms (e.g., carbon atoms, or a mixture of carbon atoms and heteroatoms), 2 to 20 atoms or 3 to atoms. Non-limiting examples of specific structures include:

where R₅o, R51, R52, and R53 are as previously defined, or

where Y and X are (0,0), (S,S), or (0,S) and R53 is as previously defined.

It should be understood that while not shown as substituted, the ring structures (XXV) and (XXVI) can be substituted as defined for structures (XX) and (XXII). In a particular instance, R₅₃ in ligand (XXVI) is hydrogen and structures (XXVI) are as follows:

d. (N, Carbene) Ligands

[0051] Suitable (N, carbene) bidentate coordinating ligands can include carbenes in a nitrogen heterocyclic ring (N, Ν,Ν-carbene) and/or sulfur heterocyclic ring(N, N,S-carbene). A (N, Ν,Ν-carbene carbene) bidentate coordinating ligand can have the following general structure:

where R₆₀, R₆₁, R₆₂, R₆₃, R₆₄, R₆₅, R₆₆, R₆₇, and R₆₈ can each independently be H, alkyl, branched alkyl groups, substituted alkyl, aryl, substituted aryl, alkoxy, heterocyclic, or heteroaryl, and X is N or S, or R₆₀ and R51, R₆₂ and R54, R54 and R57, R₆₆ and R₆₈, or R₅₇ and R₅₈, or any combination thereof can come together with other atoms to form cyclic, aryl, heterocyclic, heteroaryl rings, or R₆₀, R₆₁, R₆₄, R₆₇, and/or R₆₈ can come together to form a fused ring system, or R₆₈ is an electron pair and R₆7 together with other atoms can form a heterocyclic or heteroaryl ring system, or R₆₈ is an electron pair and R₆₀, R₅₁, R₅₄ and/or R₅₇ together with other atoms can form a heterocyclic or heteroaryl ring system, and/or R52 and R₆4 form a chemical bond or R52 R₆3, R₆₄, and R₆₅ form a double bond. The alkyl or branched alkyl groups can have a carbon number from 1 to 10, preferably 1 to 5, more preferably 1 to 3. Non-limiting examples of specific coordinating ligands are:

where R₆₀, R₆₁, R₆₂, R₆₃, and R₆₄, are as defined above and R₆₉, R70, R71, and R₇₂, can each independently be H, alkyl, branched alkyl, substituted alkyl, aryl, substituted aryl, alkoxy, heterocyclic, or heteroaryl groups, or R₆₆ and R₇₂, R₇₂ and R₇₁, R₇₁ and R₇₀, or R₇₀ and R59, can come together with other atoms to form cyclic, aryl, heterocyclic, heteroaryl rings, or R50, R51, R₅₆, and/or R59 can come together to form a fused ring system. In a particular instance, structure (XXX) has the specific structure:

[0052] In some instances, a bidentate carbene ligand is used. By way of example, a bidentate carbene can have the following generic structure:

where X and Y are each independently N, S, O, A is a hydrocarbon linking unit having 1 to 5 carbons, R50, R51, R52, R53, R54, R₆₆, R57, are as defined above for structure (XXX), and R₇₃, R₇₄, R₇₅, R₇₆, R₇₇, R₇₈, and R₇₉ can each independently be H, alkyl, branched alkyl groups, substituted alkyl, aryl, substituted aryl, alkoxy, heterocyclic, or heteroaryl, or R50 and R51, R52 and R₆₄, R₇₃ and R₇₄, R₇₄ and R_75; R₇₅ and R₇₆, or any combination thereof, can come together with other atoms to form cyclic, aryl, heterocyclic, heteroaryl rings, or R50, R51, R54, R79, and/or R₇₅ can come together to form a fused ring system. The alkyl or branched alkyl groups can have a carbon number from 1 to 10, preferably 1 to 5, more preferably 1 to 3. In a particular instance, structure (XL VI) can have the specific structure:

e. Monodentate Ligands

[0053] Monodentate ligands can include one coordinating heteroatom. Two monodentate ligands are required to coordinate with metal of the metal carboxylation catalyst as each ligand coordinates once to the metal center. Suitable monodentate ligands have the generic structure:

where X is a nitrogen (N), sulfur (S), or oxygen (O) atoms, and R₈₀, R₈₁, and R₈₂ can each be independently hydrogen, alkyl, cycloalkyl or aryl.

2. Metal Carboxylation Catalyst

[0054] The metal carboxylation catalyst can include one or more transition metals from Columns 4 through 12 of the Periodic Table. Non-limiting examples of transition metals include nickel (Ni), palladium (Pd), platinum (Pt), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), iron (Fe), ruthenium (Ru), cobalt (Co), iridium (Ir) and rhodium (Rh). The metals used to prepare the catalyst of the present invention can be provided in various oxidation states (e.g., 0, +1, +2, +3, etc.). The metal carboxylation catalyst can include a ligand L that can be displaced by the alkene. Alternatively, a metal carboxylation catalyst/coordination ligand/alkene complex can be obtained initially by reacting a transition metal source with a coordinating ligand and an alkene to give a metal carboxylation catalyst/coordination ligand/alkene complex. The metal carboxylation catalyst can include one or more ligands selected from halides, amines, amides, oxides, phosphides, carboxylates, acetylacetonate, aryl- or alkyl sulfonates, hydride, CO, olefins, dienes, cycloolefins, nitriles, aromatics and heteroaromatics, ethers, PF₃, phospholes, phosphabenzenes, and mono-, di- and polydentate phosphinite, phosphonite, phosphoramidite and phosphite ligands. Non-limiting examples of stabilizing ligands include cycloocta-1,3- diene (COD), bis(cyclooctatetraene), bis(cycloocta-l,3,7-triene), bis(o-tolylphosphito) metal (ethylene), tetrakis (triphenylphosphite) bis(ethylene), 4-butyl-naphthalene-l,2-bisolate, 1- methyl-naphthalene-l,2-bisolate, 4-ethyl catecholate, 3,5-di(butyl)-4-(bromo)catecholate, 4- (propyl)catecholate, halides (e.g., bromides and chlorides) or combinations thereof. The metal carboxylation catalyst can be prepared by known methods or purchased from a commercial supplier. Useful transition metal sources include commercial standard complexes, for example [M(p-cymene)Cl₂]₂, [M(benzene)Cl₂]n, [M(COD)2], [M(CDT)], [M(C₂H₄)₃], [MC1₂ x H₂0], [MC1₃ x H₂0], [M(acetylacetonate)₃], [M(DMS0)₄MC1₂], where M is the transition metal. In a particular embodiment, nickel(bis(cycloocta-l,5-diene) can be used as the metal carboxylation catalyst. A non-limiting example of a commercial source of the above mentioned metals or metal complexes is Sigma Aldrich® (U.S. A).

3. Alkenes and Carbon dioxide

[0055] Alkenes used in the invention can be obtained from various commercial or natural sources or be a by-product of a hydrocarbon process (e.g., hydrocracking, etc.). Suitable alkenes are those of the structure XXXVIII.

where R°, R^h, R^c, and R^d are each independently hydrogen, Ci-i₂-alkyl, C₂-i₂-alkenyl, or R^a and R* together with the other atoms to which they are bonded are a mono- or di- ethylenically unsaturated, 5- to 8-membered carbocycle, with the proviso that at least one R^a, R^h, R^c, and R^d is hydrogen. Non-limiting examples of alkenes include ethene, propene, isobutene, butadiene, piperylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1- nonene, 1-decene, styrene, substituted styrene, or combinations thereof. The alkene to be used in the carboxylation can be in a gaseous or liquid phase under the reaction conditions. In one or more embodiments, the alkene is ethylene (ethene).

[0056] Carbon dioxide used in the present invention can be obtained from various sources. In one non-limiting instance, the carbon dioxide can be obtained from a waste or recycle gas stream (e.g., from a plant on the same site, like for example from ammonia synthesis) or after recovering the carbon dioxide from a gas stream. A benefit of recycling such carbon dioxide as a starting material in the process of the invention is that it can reduce the amount of carbon dioxide emitted to the atmosphere (e.g., from a chemical production site). The C0₂ stream can be include other gases that are inert, such as helium (He), argon (Ar), or nitrogen (N₂), and do not negatively affect the reaction. The carbon dioxide stream can include the alkene. The amount of C0₂ in the reactant stream can range from 2 vol.%, 3 vol.%, 4 vol.%, 5 vol.%, 10 vol.%, 15 vol.%, 20 vol.%, 25 vol.%, 30 vol.%, 35 vol.%, 40 vol.%, 45 vol.%, 50 vol.%, 55 vol.%, 60 vol.%, 65 vol.%, 70 vol.%, 75 vol.%, 80 vol.%, 85 vol.%), 90 vol.%), 95 vol.%), 98 vol.% or any range or value there between. The amount of alkene in the reactant stream can range from 2 vol.%, 3 vol.%, 4 vol.%, 5 vol.%, 10 vol.%, 15 vol.%, 20 vol.%, 25 vol.%, 30 vol.%, 35 vol.%, 40 vol.%, 45 vol.%, 50 vol.%, 55 vol.%, 60 vol.%, 65 vol.%, 70 vol.%, 75 vol.%, 80 vol.%, 85 vol.%, 90 vol.%, 95 vol.%, 98 vol.% or any range or value there between. A volume ratio of C0₂ to alkene can range from 0.02: 1 to 40: 1. 0.02. In some instances, the reactant feed stream can include 2.5 vol.% C0₂ and 95.5 vol.% alkene, 25% vol.% C0₂ and 75 vol.% alkene, 50 vol.% C0₂ and 50 vol.% alkene, 75 vol.%) C0₂ and 25 vol.% alkene or 97.5 vol.% C0₂ and 2.5 vol.% alkene. In a particular instance, 4 vol.% C0₂ and 96 vol.% ethylene, 50 vol.% C0₂ and 50 vol.% ethylene, or 75 vol.% C0₂ and 25 vol.% ethylene.

4. Lewis Acids, Bases, Reducing Agents, and Solvents [0057] Lewis acids, inorganic bases, organic bases independently or together can be used in the reaction to promote the decomposition of any metallocycle or other metallic intermediates formed (See, for example, reaction scheme in the Method Section). These compounds can be obtained from various commercial sources. A non-limiting example of a commercial source of the Lewis acids, bases, reducing agents, and solvents is Sigma Aldrich® (U.S. A). The Lewis acid can include any compound capable of accepting an electron pair from a donor compound. Non-limiting examples of Lewis acids include, zinc, Column 1 metals, Column 2 metals, and ammonium or salts thereof. In one instance, the Lewis acid can include halogen salts {e.g., Znl₂, ZnCl₂ , ZnBr Nal, LiCl, LiBr, Lil, Me₄NCl, Me₄PCl or (Bu)₄NI, or combinations thereof). In some embodiments, halides iodides or bromides can be used, for example, Znl₂, ZnBr LiBr, Nal and/or Lil, with lithium iodide (Lil) being preferred.

[0058] Bases can include inorganic anionic bases or organic bases that bind to protons (H+) generated in the reaction. In some embodiments, the base can have a pKa between 7 and 13. Non-limiting examples of inorganic bases include carbonates, phosphates, nitrates or halides of Column 1 and 2 metals (e.g., NaOH, Na₂CO₃, NaHCO₃, Li OH, Li₂CO₃, LiHCO₃, etc.), zinc, reactive metal compounds {e.g., trimethyl aluminum) or combinations thereof. Non-limiting examples of organic bases include alkoxides, phenolates, carboxylates, sulfates, sulfonates, phosphates, phosphonates, ethers, esters, imines, amides, carbonyl compounds (e.g., carboxylates or carbon monoxide), and primary, secondary or tertiary amines, bipyridyls (e.g., 4,4'-bipyridyl) or substituted bipyridyls (e.g., ring or heteroatom substituted). In one instance, triethylamine can be used.

[0059] Reducing agents can be used to reduce the metal carboxylation catalyst to its lowest oxidation state after forming a metallocycle or other ligand/catalyst/alkene complex, thereby promoting a cyclic reaction. Reducing agents can include zero oxidation state metals (e.g., zinc) and/or reducible organic compounds (e.g., hydroquinone or aminophenol). The reducing agent can be supplied in the form of powder, pellets or granules.

[0060] A suitable solvent is one in which the transition metal complex has good solubility. Examples include aromatic hydrocarbons, halogenated aromatic hydrocarbons, ethers (e.g., tetrahydrofuran), alcohols, dimethylformamide, dimethyl sulfoxide, water, or any mixtures thereof. Non-limiting examples of aromatic hydrocarbons include benzene, toluene xylene, or mixtures thereof. Non-limiting examples of halogenated aromatic hydrocarbons include chlorobenzene, fluorobenzene, or mixtures thereof. Non-limiting examples of alcohols include methanol, ethanol, isopropanol, or mixtures thereof. Non-limiting examples of aliphatic solvents include pentane, hexane, heptane, or mixtures of thereof.

B. Method of Making an α,β-Unsaturated Carboxylic acids or Salts thereof.

[0061] α,β-Unsaturated carboxylic acids or salts thereof can be made in a catalytic manner using a transition metal carboxylation catalyst in the presence of a coordinating ligand. FIG. 1 is a schematic of the catalytic cycle to make α,β-unsaturated carboxylic acids or salts thereof using the coordinating ligands of the present invention. In step 1 of the method 100, a metal carboxylation catalyst and a coordinating ligand of the present invention in a solvent can be obtained. A base described above can be added to the solution (composition). Without wishing to be bound by theory, it is believed that the reaction can be made more exergonic by addition of a base that helps promote regeneration of the metal and/or inhibit the formation of propionate salts. In some embodiments, base is not used. The metal carboxylation catalyst/coordinating ligand complex and solvent can be a homogeneous or heterogeneous mixture. In a particular embodiment, the solvent and metal carboxylation catalyst/coordinating ligand complex form a homogeneous mixture. [0062] The alkene (e.g., Structure XXXVIII, where R^rf is hydrogen) and carbon dioxide can be added to this mixture and the mixture can be subjected to temperatures and pressures suitable to form the metallocycle compound 102. The alkene and the carbon dioxide can be added together or separately. In a particular embodiment, the alkene is added first and then the carbon dioxide can be added to the solution. In certain embodiments, the addition of the alkene can be carried out at room temperature, followed by addition of carbon dioxide at a higher temperature than room temperature, preferably at a temperature between 25 °C and 75 °C, preferably from 30 °C to 50 °C. The reaction can be performed under an alkene/carbon dioxide atmosphere.

[0063] In step 2, a Lewis acid can be added to the metallocycle mixture. Without wishing to be bound by theory, it is believed that the Lewis acid facilitates opening of the metallocycle to form a α,β-unsaturated carboxylic acid-metal complex 104. As shown, the metal is complexed with the olefin portion of complex 104 and the Lewis acid is complexed with the carboxylic acid.

[0064] In step 3, a reducing agent can be added to reduce the metal complex to its zero valence, which frees the α,β-unsaturated carboxylic acid salt compound 106 from the metal complex. The reduced (regenerated) metal complex 108 can then be used to react with more carbon dioxide and alkene to continue the cycle. In some embodiments, a reducing agent is not necessary. In a particular embodiment, steps 1, 2, and 3 are done simultaneously at temperatures and pressures suitable to form and decompose the metallocycle compound 102, and then release the α,β-unsaturated carboxylic acid salt 106 from the α,β-unsaturated carboxylic acid-metal complex 104. [0065] Reaction conditions can include any temperature and pressure. For example, the reaction can be carried out at normal pressure, a partial pressure of 0.1 to 10 MPa (1 to 100 bar), 0.3 to 5 MPa, 0.2 to 10 MPa, or 0.5 to 3 MPa and/or a partial pressure of 0.1 to 10 MPa, 0.2 to 10 MPa, 0.5 to 5 MPa, or 1 to 3 MPa of the corresponding alkene. In some embodiments, the alkene is solubilized in the solvent and the reaction is run under a carbon dioxide atmosphere. A reaction temperature can range from 0 to 150 °C, 15 to 100 °C or 20 to 60 °C. In some embodiments, the Lewis acid is not used and α,β-unsaturated carboxylic acid salt 106 is a carboxylic acid. In a particular instance, steps 1, 2, and 3 are all performed simultaneously. In some embodiments, metallocycle compound 102 is isolated after step 1 and then subjected to conditions suitable to decompose the metallocycle compound to the corresponding carboxylic acid 110.

[0066] The compound 106 can be converted to a free carboxylic acid 110 and/or subjected to: acylating conditions to produce esters, amides or the like; polymerized to produce polyacrylates; or polymerized with other monomers/polymers to produce acrylate co-polymers. Non-limiting examples of esters made from acrylic acid and alcohols are shown in FIG. 2.

EXAMPLES

[0067] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results. Examples 1-15

(Method of Making Acrylic Acid)

[0068] Examples 1-16 were performed using the coordinating ligands of the present invention listed in Table 1 and the following general procedure. All materials were obtained from Sigma-Aldrich® (USA). [0069] General Procedure. In a 10 mL vial, equipped with a small stirring bar, a ligand from Table 1 and the compounds from Table 2 (e.g., bis(l,5-cyclooctadiene)nickel(0) (Ni(COD)₂), and lithium iodide (Lil) and, optionally, zinc (Zn)) were suspended in a solvent (flourobenzene (PhF) or chlorobenzene). To the solution triethylamine (NEt₃) was added, the vial was capped with a septum seal, and the septum was perforated with a needle that was kept in place. The vial was placed in a Parr autoclave, heated to 50 °C by placing the autoclave in an oil bath kept at that temperature, pressurized to a desired pressure using ethylene, and subsequently further pressurized to a desired pressure with C0₂. The solution was stirred for 24 hours at this pressure and temperature. After a desired amount of time, the heating was turned off, the autoclave was vented and cooled over 30 minutes and then the sample was removed from the autoclave. The clear reaction mixture (solution) turned from reddish purple to the color listed in Table 2. The vial was opened, lithium acetate dihydrate LiOAc^»2H₂0 was added to the flask, and then about 1 mL of water was added. Deuterated water D₂0 was used instead of H₂0, for NMR analysis. The content of the flask was vigorously shaken to dissolve all the salts in the water layer. Solids were separated from the solution, and the water layer was separated from the chlorobenzene layer. 1H NMR analysis of the water layer using a Bruker 400 MHz was performed. In all Examples, from the NMR analysis, it was determined that acrylic acid was formed. [0070] Reaction Vessel General Procedure. Lithium iodide (Lil, 163 mg) and zinc (Zn, 50 mg) dust as the reducing agent were added to a reaction vessel. Then a solution of the metal carboxylation catalyst (7 mg bis(cycloocta-l,5-diene)nickel (Ni(C₈H₁₂)₂)), and a ligand of the present invention listed in Table 1 (1 : 1 mixture based on the nickel catalyst) in chlorobenzene (C₆H₅C1, 2.5 mL) was added to the reaction vessel. Base (triethylamine, (N(C₂H₅)₃), 126 mg) was added to the reaction vessel. The reaction vessel was equipped the vessel with an agitation device. With stirring, the reaction vessel was then pressurized with 15 bar ethylene. After 5 minutes of stirring at room temperature, the flask was charged with C0₂ to a final pressure of 30 bar, the temperature was raised to 50 °C and under these conditions was stirred for a further 24 hours. After 24 hours the vessel was opened, LiOAc.₂H₂0 (20 mg) was added as internal standard, and 1 mL of D₂0 to solubilize the salts. The D₂0 layer was analyzed by MR, revealing trace amounts of acrylate ion.

Table 1

Example 20

(Theoretical Calculations of Transition State Energies for Ligands of the Present

Invention and Phosphine Ligands)

[0071] Theoretical calculations we performed using a Gaussian g09 program. All calculations were performed using density functional theory method DFT b31yp/6-31g** basis set while the metal center was defined using pseudo potential SDD. The final energies were computed with triple zeta quality (TZVP) basis sets along with pseudo potential SDD for metal center. The polar continuum model (PCM) was used to taken in account the effect of toluene and flourobenzene solvent environment. FIG. 3 depicts a diagram for the reaction pathways and transition that can be formed during catalysis of an alkene with carbon dioxide. Calculated energy values are listed in Tables 3 and 4. As shown in FIG. 3, the metallocycle (M2) has the lowest transition state, thus this it is believed that the metallocycle (M2) structure is formed as a preferred intermediate structure. Decomposition of the metallocycle (M2), formed from the oxidative coupling of a metal olefin adduct (Ml to Tl-2 to M2), was calculated to have three transition state keto-enol structures T2-3A, T2-3B and T2-3C, with T2-3C having the lowest energy of the three possible transition states (i.e., T2-3A > T2-3B > T2-3C in energy).

[0072] For the conventional l,2-(bisdicyclohexylphsphino)ethane (dcpe) ligand (shown below) and nickel, the energy barriers (kcal/mol) listed in Table 3 were calculated for the system without any additional reagents, and with Lil, with NEt₃, and with both Lil and NET₃. For the ligands of the current invention (compound VI) and nickel, the energy barriers (kcal/mol) listed in Table 4 were calculated for the system without any additional reagents, and with Lil, with NEt₃, and with both Lil and NET₃. Comparing Table 3 and Table 4 energy barriers, it was determined that the enolisation transition state, T2-3C, with diimine ligand VI was about 5 kcal/mol lower than the same barrier with the diphosphine ligand. Overall, the diimine ligand VI, had enolisation transition states lower in energy than the oxidative coupling transition states, which results in driving forward for the reaction. Thus, it can be concluded that the use of dinitrogen ligands are beneficial for driving the reaction forward.

[0073] Other metals. For the same reaction, calculations were performed using palladium instead of nickel. In the β-hydrogen elimination reaction, T2-3B, become kinetically more favorable, but the enolisation transition, T2-3C, lead to a product, M3C, that was thermodynamically more stable than the starting metallolactone (M2). Under conditions where M2 can form (i.e. where transition state Tl-2 at 32.2 kcal/mol can be overcome), also barrier T2-3C (at the very similar 32.7 kcal/mol) can be overcome. M3C was predicted to be the thermodynamically favored product. Thus, the pathway to the thermodynamically a productive cycle may be possible with Pd metal and dinitrigen ligands.

Claims

1. A method of making an α,β-unsaturated carboxylic acid or a salt thereof, the method comprising: reacting an alkene and carbon dioxide with a composition comprising a metal containing carboxylation catalyst and a coordinating ligand under conditions suitable to produce the α,β-unsaturated carboxylic acid or salt thereof, wherein the coordinating ligand comprises at least two coordinating atoms selected from nitrogen (N), oxygen (O), sulfur (S), and carbene that coordinate with the metal in the carboxylation catalyst.

2. The method of claim 1, wherein the at least two coordinating atoms are different.

3. The method of claim 1, wherein the at least two coordinating atoms are the same.

4. The method of claim 3, wherein the at least two coordinating atoms are each nitrogen.

5. The method of claim 4, wherein the coordinating ligand has a general structure of:

where R₁, R₂, R₃ and R₄ are each independently a hydrogen, an alkyl, a branched alkyl, a cycloalkyl, an aryl, a substituted aryl, a substituted heteroatom, a heterocyclic, a halogen, a heterocyclic or a heteroaryl group, or where R₁ and R₂, R₂ and R_3, and/or R₃ and R₄ come together with other atoms to form a cycloalkyl, cycloalkenyl, aryl, heteroaryl, or heterocyclic ring.

6. The method of claim 5, wherein R₁ and R₄ are each independently an alkyl, a branched alkyl, a cycloalkyl, an aryl, or a substituted aryl group.

7. The method of claim 5, wherein R₂ and R₃ come together with other atoms to form a cycloalkyl, cycloalkenyl, aryl, heteroaryl, or heterocyclic ring.

8. The method of any one of claims 5 to 7, wherein R₁ and R₂ come together to form a heteroaryl or heterocyclic ring, and R₃ and R₄ are each independently a hydrogen, an alkyl, a branched alkyl, a cycloalkyl, an aryl, a substituted aryl, a heteroaryl group or come together to with other atoms to form a heteroaryl or heterocyclic ring.

9. The method of claim 5, wherein the coordinating ligand has the general structure of:

where R₅, R₆, R₇, R₈, R₉, R₁₀, R11, R12, R13, and R14 are each independently H, alkyl, or branched alkyl, substituted aryl, or substituted heteroatom groups, wherein the alkyl or branched alkyl groups have a carbon number from 1 to 10, preferably 1 to 5, more preferably 1 to 3.

10. The method of claim 9, wherein R₅, R_9; R₁₀, and R14 are each independently hydrogen (H), methyl (CH₃) or isopropyl ((CH₃)₂CH) groups, or combinations thereof.

11. The method of claim 9, wherein the coordinating ligand is selected from the group consisting essentially of:

12. The method of claim 5, wherein the coordinating ligand is:

13. The method of claim 5, where the coordinating ligand is selected from the group consisting essentially of:

14. The method of claim 1, wherein the composition further comprises a Lewis acid, a base, a reducing agent, base, or any combination thereof.

15. The method of claim 14, wherein the Lewis acid is a salt of a metal from Columns 1 or 2 of the Periodic Table.

The method of any one of claims 14 to 15, wherein the reducing agent is zinc or an organic reducing agent, preferably hydroquinone or aminophenol.

The method of any one of claims 14 to 16, wherein the base is a hydroxide, a carbonate, a bicarbonate, a phenoxide, an alkoxide, or an amino salt of a Columns 1 or 2 metal.

18. The method of any one of claims 1 to 18, wherein the carboxylation catalyst metal comprises at least one transition metal, preferably, nickel (Ni) or palladium (Pd).

19. The method of any one of claims 1 to 18, wherein the carboxylation catalyst is bis(cycloocta-l,5-diene)nickel and the coordination ligand reacts with the carboxylation catalyst to form a (cycloocta-l,5-diene)nickel— coordination ligand complex.

20. The method of any one of claims 1 to 19, wherein the alkene is ethylene, propylene, or styrene, and the carboxylic acid is acrylic acid, methacrylic acid, or cinnamic acid, or salts thereof.