JP6890320B2 - Catalyst used for hydrogenation of carbon dioxide, formic acid production method, hydrogen storage method - Google Patents

Description

The present invention relates to a catalyst used for hydrogenation of carbon dioxide, a method for producing formic acid, and a method for storing hydrogen.

The development of carbon dioxide emission reduction technology is an urgent issue. Hydrogen (H ₂ ) is attracting attention as a clean energy in the future, but it is difficult to transport and store, and safe and low-cost transportation and storage technology is required.

In order to solve the problems of effective use of carbon dioxide or hydrogen transportation / storage technology, a method of storing hydrogen as a fuel such as formic acid obtained by hydrogenating carbon dioxide has been considered. Formic acid (HCOOH), which is liquid at room temperature and has relatively low toxicity, has recently attracted attention as a hydrogen storage material because it can be interconverted with _{hydrogen (H 2} ) / carbon dioxide (CO _2). However, in the conventionally known methods using catalysts and the like, these reactions are multi-energy consumption processes. For example, _{the synthesis of formic acid or formate by CO 2} hydrogenation generally requires a high temperature and high pressure reaction. Therefore, it has been desired to develop a high-performance catalyst capable of producing formate from carbon dioxide under mild conditions.

Since the 1960s, _{the formation of formic acid or formate by the hydrogenation reaction of CO 2 with} a metal complex catalyst has been known, but in recent years, catalysts that act in water without using organic solvents or organic additives have been reported (Patent). Documents 1 to 7 and Non-Patent Documents 1 to 4). Recently, catalysts capable of producing formic acid or formate even under normal temperature and pressure reaction conditions in water have been reported. (Patent Documents 7 to 8, Non-Patent Documents 8 to 17)

So far, complexes using picoline amide as a ligand are known (Patent Documents 9 to 10 and Non-Patent Documents 18 to 19), but there have been no examples of using these as hydrogenation catalysts for carbon dioxide.

Japanese Patent No. 3968431 Japanese Patent No. 409728 Japanese Patent No. 4822253 PCT / IB2015 / 059242 specification Japanese Patent No. 581290 WO2013 / 040013 (Patent No. 6071079) Japanese Patent Application No. 2016-217789 WO2011 / 108730 specification US2010 / 0234596A1 (Patent No. 5719115) Japanese Unexamined Patent Publication No. 2012-62270

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An object of the present invention is to provide a high-performance catalyst for producing formic acid and / or formate by highly efficient hydrogenation of carbon dioxide.
Another object of the present invention is to provide a highly efficient method for producing formic acid and / or formate using the catalyst.

The present inventors have previously found that a complex catalyst using a ligand consisting of a nitrogen-containing 5-membered ring skeleton exhibits high catalytic activity in hydrogenation of carbon dioxide (Patent Documents 1 to 7). ). However, the elaborate ligand structure has limited changes in the ligand structure for further activation. Therefore, the present inventors recognized the need for a highly active new catalytic ligand that has a simpler structure and is easier to synthesize. As a result of diligent research to solve the above problems, the complex catalyst represented by any of the general formulas (1) to (5) is effective for the production of formic acid and / or formate by hydrogenation of carbon dioxide. The present invention has been completed, and the present invention comprises the following technical means.

一般式(１)において、
Mは、イリジウム、ロジウムまたはルテニウムであり、
Lは、芳香族性アニオン配位子、または芳香族性配位子であり、置換基を有している場合は、前記置換基は１つでも複数でも良く、
Jは、任意の配位子であるか、または存在せず、
Xⁱ(iは、１または２)は、窒素、酸素、硫黄、炭素のいずれかであり、Xⁱが窒素の場合は単結合で結合した置換基Qⁱを有しても良く、Xⁱが炭素の場合は単結合または二重結合で結合された置換基Qⁱを有しても良く、
X¹ とX²は単結合または二重結合で結合し、
Qⁱ(iは１または２)は、Xⁱと単結合で結合する場合、水素原子、アルキル基、ヒドロキシ基、アルコキシ基、オキシアニオン基、オキソ基、ニトロ基、ハロゲン基、スルホン基、アシル基、カルボン酸基もしくはその誘導体、アミノ基、アルキルアミノ基、アミド基、またはフェニル基であり、Xⁱが炭素の場合Qⁱは２つまで存在可能であり、QⁱがXⁱと二重結合で結合する場合、Qⁱは、酸素(＝O)、硫黄(＝S)、窒素(＝NR)、または炭素(＝CRR’)であり、窒素、または炭素の場合さらに置換基(RもしくはR’)を有しても良く、
Q¹ とQ²が置換基を通して結合しで環を形成しても良く、
Zは、酸素、硫黄のいずれかであり、
Tは、水素原子、または任意の置換基であり
nは、金属錯体の電荷を表し、正の整数、０、または負の整数である。
＜２＞一般式(２)で表され、Y¹-Y²-C(＝O)-N-TのY¹と窒素で配位し、環構造を有する二座配位子を有する金属錯体、その異性体、または塩を有効成分として含む、二酸化炭素の水素化によるギ酸および／またはギ酸塩を製造するための触媒。

一般式(２)において、
Mは、イリジウム、ロジウム、ルテニウムのいずれかであり、
Lは、芳香族性アニオン配位子、または芳香族性配位子であり、置換基を有している場合は、前記置換基は１つでも複数でも良く、
Jは、任意の配位子であるか、または存在せず、
Y¹は、窒素、酸素、硫黄、炭素のいずれかであり、
Y²は、窒素または炭素であり、
Y¹とY²は、単結合または二重結合で結合し、Y¹とY²の間の環上に置換基を有しても良く、
Tは、水素原子、または任意の置換基であり、
nは、金属錯体の電荷を表し、正の整数、０、または負の整数である。
＜３＞一般式(１)または(２)のMがイリジウムであり、Lがペンタメチルシクロペンタジエニル配位子である＜１＞または＜２＞に記載の二酸化炭素の水素化によるギ酸および／またはギ酸塩を製造するための触媒。
＜４＞一般式(３)で表され、アミド窒素と６員環上の窒素もしくは炭素で配位する二座配位子を有する金属錯体、その異性体、または塩を有効成分として含む、二酸化炭素の水素化によるギ酸および／またはギ酸塩を製造するための触媒。

一般式(３)において、
Jは、任意の配位子であるか、または存在せず、
Y¹は、窒素または炭素であり、
Y²は、窒素または炭素であり、
A¹〜A⁴は、それぞれ独立に、酸素、硫黄、窒素、炭素のいずれかであり、
Y¹、Y²およびA¹〜A⁴から構成される６員環のそれぞれの原子は単結合、二重結合で結合、または芳香環を形成し、
R¹〜R⁴は、それぞれ独立に、水素原子、アルキル基、ヒドロキシ基、アルコキシ基、オキシアニオン基、オキソ基、ニトロ基、ハロゲン基、スルホン基、アシル基、カルボン酸基もしくはその誘導体、アミノ基、アルキルアミノ基、アミド基、またはフェニル基であり、置換基を有していても良く、置換基を有している場合は、前記置換基は１つでも複数でも良く、(ただし、Aⁱ(iは１〜４の整数)が酸素または硫黄である場合その位置のRⁱは存在せず、Aⁱが窒素の場合は最大１つの置換基Rⁱを有することも可能であり、Aⁱが炭素の場合は最大２つの置換基Rⁱまたは二重結合で結合された１つの置換基を有することも可能である。)
Tは、水素原子、または任意の置換基であり、
nは、金属錯体の電荷を表し、正の整数、０、または負の整数である。
＜５＞一般式(４)で表され、アミド窒素と５員環から成る二座配位子を有する金属錯体、その異性体、または塩を有効成分として含む、二酸化炭素の水素化によるギ酸および／またはギ酸塩を製造するための触媒。

一般式(４)において、
Jは、任意の配位子であるか、または存在せず、
Y¹は、窒素、酸素、硫黄、炭素のいずれかであり、
Y²は、窒素または炭素であり、
A⁵〜A⁷は、それぞれ独立に、酸素、硫黄、窒素、炭素のいずれかであり、
Y¹、Y²およびA⁵〜A⁷から構成される５員環のそれぞれの原子は単結合、二重結合で結合し、または芳香環を形成し、
R⁵〜R⁷は、それぞれ独立に、水素原子、アルキル基、ヒドロキシ基、アルコキシ基、オキシアニオン基、オキソ基、ニトロ基、ハロゲン基、スルホン基、アシル基、カルボン酸基もしくはその誘導体、アミノ基、アルキルアミノ基、アミド基、またはフェニル基であり、置換基を有していても良く、置換基を有している場合は、前記置換基は１つでも複数でも良く、(ただし、Aⁱ(iは５〜７の整数)が酸素または硫黄である場合、その位置のRⁱは存在せず、Aⁱが窒素の場合は最大１つの置換基Rⁱを有することも可能であり、Aⁱが炭素の場合は最大２つの置換基Rⁱまたは二重結合で結合された１つの置換基を有することも可能である。)
Tは、水素原子、または任意の置換基であり、
nは、金属錯体の電荷を表し、正の整数、０、または負の整数である。
＜６＞一般式(５)で表され、アミド窒素と芳香族含窒素６員環上の窒素で配位する二座配位子を有する金属錯体、その異性体、または塩を有効成分として含む、二酸化炭素の水素化によるギ酸および／またはギ酸塩を製造するための触媒。

一般式(５)において、
Jは、任意の配位子であるか、または存在せず、
Tは、水素原子、または任意の置換基であり
A⁸およびA⁹は、それぞれ独立に、窒素または炭素であり、
R⁸およびR⁹は、それぞれ独立に、水素原子、アルキル基、ヒドロキシ基、アルコキシ基、オキシアニオン基、ニトロ基、ハロゲン基、スルホン基、アシル基、カルボン酸基もしくはその誘導体、アミノ基、アルキルアミノ基、アミド基、または、置換基を有しているか有していないフェニル基であり、
nは、金属錯体の電荷を表し、正の整数、０、または負の整数である。
＜７＞一般式(１)〜(５)のいずれかにおいて、Jが、水分子、水素原子、アルコキシドイオン、水酸化物イオン、ハロゲン化物イオン、炭酸イオン、トリフルオロメタンスルホン酸イオン、硫酸イオン、硫酸水素イオン、硝酸イオン、ギ酸イオン、もしくは酢酸イオンであるか、または存在しない＜１＞〜＜６＞のいずれか１項に記載の二酸化炭素の水素化によるギ酸および／またはギ酸塩を製造するための触媒。
＜８＞＜１＞〜＜７＞のいずれか１項に記載の触媒の存在下、水素と二酸化炭素を反応させて、ギ酸および／またはギ酸塩を製造する二酸化炭素の水素化方法。
＜９＞＜１＞〜＜７＞のいずれか１項に記載の触媒の存在下、水素と二酸化炭素を反応させて、ギ酸および／またはギ酸塩を製造することによる水素の貯蔵方法。 <1> is represented by the general formula (1), coordination metal complexes by X ¹ and nitrogen bidentate ligand ^{(X 1 -X 2 -C (=} Z) -NT) (N), its isomers , Or a catalyst for producing formic acid and / or formate by hydrogenation of carbon dioxide, which comprises a salt as an active ingredient.

In the general formula (1)
M is, iridium, rhodium or ruthenium-time,
L is an aromatic anion ligand or an aromatic ligand, and when it has a substituent, the substituent may be one or more.
J is any ligand or does not exist,
X ⁱ (i is 1 or 2) is any of nitrogen, oxygen, sulfur, and carbon, and when X ⁱ is nitrogen, it may have a substituent Q ⁱ bonded in a single bond, and X ⁱ If is carbon, it may have a substituent Q ⁱ bonded by a single bond or a double bond.
X ¹ and X ² are single-bonded or double-bonded,
When Q ⁱ (i is 1 or 2) is ^{bonded to X i} by a single bond, hydrogen atom, alkyl group, hydroxy group, alkoxy group, oxyanion group, oxo group, nitro group, halogen group, sulfone group, acyl A group, a carboxylic acid group or a derivative thereof, an amino group, an alkylamino group, an amide group, or a phenyl group. ^{If X i} is carbon, ^{up to two Q i} can exist, and Q ⁱ is double with X ^i. When bonded by bond, Q ⁱ is oxygen (= O), sulfur (= S), nitrogen (= NR), or carbon (= CRR'), and in the case of nitrogen, or carbon, further substituents (R or May have R')
Q ¹ and Q ² may be bonded through a substituent to form a ring.
Z is either oxygen or sulfur,
T is a hydrogen atom, or any substituent
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer.
<2> A metal complex represented by the general formula (2), ^{which is coordinated with Y 1 of Y 1} -Y ^2- C (= O) -NT with nitrogen and has a bidentate ligand having a ring structure. A catalyst for producing formic acid and / or formate by hydrogenation of carbon dioxide, which comprises an isomer or salt as an active ingredient.

In the general formula (2)
M is, iridium, rhodium, is any of ruthenium-time,
L is an aromatic anion ligand or an aromatic ligand, and when it has a substituent, the substituent may be one or more.
J is any ligand or does not exist,
Y ¹ is either nitrogen, oxygen, sulfur or carbon,
Y ² is nitrogen or carbon,
Y ¹ and Y ² may be single or double bonded and may have a substituent on the ring between ^{Y 1} and Y ^2.
T is a hydrogen atom, or any substituent,
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer.
<3> Formic acid and formic acid by hydrogenation of carbon dioxide according to <1> or <2>, wherein M in the general formula (1) or (2) is iridium and L is a pentamethylcyclopentadienyl ligand. / Or a catalyst for producing formate.
<4> Dioxide, which is represented by the general formula (3) and contains a metal complex having a bidentate ligand coordinated with amide nitrogen and nitrogen or carbon on a 6-membered ring, an isomer thereof, or a salt as an active ingredient. A catalyst for producing formic acid and / or formate by hydrogenation of carbon.

In the general formula (3)
J is any ligand or does not exist,
Y ¹ is a nitrogen or carbon-containing,
Y ² is nitrogen or carbon,
A ^{1 to} A ⁴ are independently one of oxygen, sulfur, nitrogen, and carbon.
Each atom of the 6-membered ring composed of Y ¹ , Y ² and A ^{1 to} A ⁴ forms a single bond, a double bond, or an aromatic ring.
R ^{1 to} R ⁴ are independently hydrogen atom, alkyl group, hydroxy group, alkoxy group, oxyanion group, oxo group, nitro group, halogen group, sulfone group, acyl group, carboxylic acid group or derivative thereof, amino. It may be a group, an alkylamino group, an amide group, or a phenyl group and may have a substituent, and when it has a substituent, the substituent may be one or more (however, A). ^{If i} (i is an integer of 1 to 4) is oxygen or sulfur, then R ^{i at} that position does not exist, and if A ⁱ is nitrogen, it is possible to have ^{up to one substituent R i, A. If i} is carbon, it is ^{also possible to have up to two substituents R i} or one substituent bonded by a double bond.)
T is a hydrogen atom, or any substituent,
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer.
<5> Formic acid by hydrogenation of carbon dioxide and a metal complex represented by the general formula (4) and having a bidentate ligand consisting of amide nitrogen and a 5-membered ring, an isomer thereof, or a salt thereof as an active ingredient. / Or a catalyst for producing formate.

In the general formula (4)
J is any ligand or does not exist,
Y ¹ is either nitrogen, oxygen, sulfur or carbon,
Y ² is nitrogen or carbon,
A ^{5 to} A ⁷ are independently one of oxygen, sulfur, nitrogen, and carbon.
Each atom of the 5-membered ring consisting of Y ¹ , Y ² and A ^{5 to} A ⁷ is single-bonded, double-bonded, or forms an aromatic ring.
R ^{5 to} R ⁷ are independently hydrogen atom, alkyl group, hydroxy group, alkoxy group, oxyanion group, oxo group, nitro group, halogen group, sulfone group, acyl group, carboxylic acid group or derivative thereof, amino. It may be a group, an alkylamino group, an amide group, or a phenyl group and may have a substituent, and when it has a substituent, the substituent may be one or more (however, A). ^{If i} (i is an integer of 5-7) is oxygen or sulfur, then R ^{i at} that position does not exist, and if A ⁱ is nitrogen, it is possible to have ^{up to one substituent R i.} If A ⁱ is carbon, it is ^{also possible to have up to two substituents R i} or one substituent bonded by a double bond.)
T is a hydrogen atom, or any substituent,
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer.
<6> A metal complex having a bidentate ligand coordinated with amide nitrogen and nitrogen on a 6-membered ring containing aromatic nitrogen, an isomer thereof, or a salt thereof, which is represented by the general formula (5), is contained as an active ingredient. , A catalyst for producing formate and / or formate by hydrogenation of carbon dioxide.

In the general formula (5)
J is any ligand or does not exist,
T is a hydrogen atom, or any substituent
A ⁸ and A ⁹ are independently nitrogen or carbon, respectively.
R ⁸ and R ⁹ are independently hydrogen atom, alkyl group, hydroxy group, alkoxy group, oxyanion group, nitro group, halogen group, sulfone group, acyl group, carboxylic acid group or derivative thereof, amino group, alkyl. An amino group, an amide group, or a phenyl group with or without a substituent,
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer.
<7> In any of the general formulas (1) to (5), J is a water molecule, a hydrogen atom, an alkoxide ion, a hydroxide ion, a halide ion, a carbonate ion, a trifluoromethanesulfonic acid ion, a sulfate ion, Produce formic acid and / or formate by hydrogenation of carbon dioxide according to any one of <1> to <6>, which is hydrogen sulfate ion, nitrate ion, formate ion, or acetate ion, or does not exist. Ion for.
<8> A method for hydrogenating carbon dioxide to produce formic acid and / or formate by reacting hydrogen with carbon dioxide in the presence of the catalyst according to any one of <1> to <7>.
<9> A method for storing hydrogen by reacting hydrogen with carbon dioxide in the presence of the catalyst according to any one of <1> to <7> to produce formic acid and / or formate.

By using the complex catalyst of the present invention, it is possible to convert hydrogen gas into formic acid or the like, which is a liquid fuel suitable for transportation and storage, by the hydrogenation reaction of carbon dioxide.

In addition, the complex catalyst of the present invention exhibits higher catalytic activity than conventional complex catalysts in the carbon dioxide hydrogenation reaction in water without using organic additives.

FIG. 1 is a graph showing the time course of the catalyst rotation speed and the production concentration of formic acid production in carbon dioxide hydrogenation under normal temperature and pressure conditions in water using the complex catalyst represented by the formula (9).

In the present invention, formic acid and / or formate refers to formic acid only, formate only, a mixture of formic acid and formate, or a mixture of formic acid and base or formate and acid.
Further, in the present specification, "~" indicating a numerical range is used to mean that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.

In the present invention, formic acid and / or formate can be efficiently produced, preferably in an alkaline aqueous solution, by the hydrogenation reaction of carbon dioxide represented by the following formula. The obtained formate can be easily converted to formic acid by treating with an acid.

In the complex catalyst represented by the general formula (1) or (2), examples of the transition metal represented by M include iridium, rhodium, ruthenium, cobalt, osmium, nickel, iron, palladium and platinum, and particularly iridium. Is preferable.

In the complex catalyst represented by any of the general formulas (1) to (5), the ligand represented by J includes a water molecule, a hydrogen atom, an alkoxide ion, a hydroxide ion, a halide ion, and a carbonate ion. , Trifluoromethanesulfonate ion, sulfate ion, hydrogen sulfate ion, nitrate ion, formate ion, or ligand of acetate ion, or may not be present. The alkoxide ion is not particularly limited, and for example, an alkoxide ion derived from methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, isobutyl alcohol, tert-butyl alcohol and the like can be used. Can be mentioned.

In the complex catalyst represented by any of the general formulas (1) to (5), substitution, elimination, etc. may be relatively easy depending on the type of ligand represented by J. As an example, the ligand J becomes a water molecule (-OH ₂ ) in an acidic aqueous solution and -OH in an alkaline aqueous solution. In addition, it easily becomes a hydrogen atom in the presence of hydrogen gas or formic acid molecule. It becomes an alkoxide ion in an alcohol solvent and may be desorbed by light or heat. However, this description is merely an example of a possible mechanism and does not limit the present invention.

In the complex catalyst represented by any of the general formulas (1) to (5), n represents the charge of the metal complex and is a positive integer, 0, or a negative integer.

In formulas (1) to (5) complex catalyst represented by any one of its counter ion is not particularly limited, as the anion, for example, hexafluorophosphate ion (PF ₆ ^-), tetra tetrafluoroborate ion (BF ₄ ^-), hydroxide ions (OH ^-), acetate ion, carbonate ion, phosphate ion, sulfate ion, nitrate ion, halide ion (e.g. fluoride ion (F ^-), chloride ion (Cl ^-), a bromide ion (Br ^-), iodide ion (I ^-), etc.), hypohalous acid ion (e.g. hypofluorite ion, hypochlorite ion, hypobromous acid ion, hypophosphite iodine Acid ion, etc.), Hypofluorous acid ion (for example, chlorofluorous acid ion, chlorate ion, bromine acid ion, iodate ion, etc.) etc. iodate ion), perhalogen acid ion (e.g., perfluorinated acid ion, perchloric acid ion, perbromic acid ion, periodic acid ion, etc.), trifluoromethanesulfonate ion (OSO ₂ CF ₃ ^-), tetrakis pentafluoro tetraphenylborate ion _{[B (C 6 F 5)} 4 -] , and the like. The cation is not particularly limited, but various metal ions such as lithium ion, magnesium ion, sodium ion, potassium ion, calcium ion, barium ion, strontium ion, yttrium ion, scandium ion, lanthanoid ion, hydrogen ion and the like can be used. Can be mentioned. Further, these counter ions may be of one type, but two or more types may coexist. However, this description is merely an example of a possible mechanism and does not limit the present invention.

In the complex catalyst represented by the general formula (1), Z is either oxygen or sulfur, preferably oxygen.

In the complex catalyst represented by the general formula (1), X ⁱ (i is 1 or 2) is any one of nitrogen, oxygen, sulfur and carbon, preferably nitrogen or carbon. Further, when X ⁱ is nitrogen, it may have a substituent Q ⁱ bonded by a single bond, and when X ^{i is carbon, it may have a substituent Q i} bonded by a single bond or a double bond. Is also good. In addition, X ¹ and X ² are bonded by a single bond or a double bond.

In complex catalyst represented by the general formula (1), Q ⁱ is X ⁱ (i is 1 or 2) that binds to a single bond, Q ⁱ is a hydrogen atom, an alkyl group, hydroxy group, alkoxy group, aryloxy Anion group, oxo group, nitro group, halogen group, sulfone group, acyl group, carboxylic acid group or derivative thereof, amino group, alkylamino group, amide group, or phenyl group, where X ⁱ is carbon and Q ⁱ is when merging with X ⁱ single bond Q ⁱ is be present up to two, if Q ⁱ where Q ⁱ is attached at X ⁱ and a double bond, an oxygen (= O), sulfur (= S), nitrogen ( = NR) or carbon (= CRR'), and in the case of nitrogen or carbon, it may further have a substituent (R or R'). Further, Q ¹ and Q ² may be bonded through a substituent to form a ring.

In the complex catalyst represented by any of the general formulas (2) , (4) and ^{(5), Y 1} is any of nitrogen, oxygen, sulfur and carbon, preferably nitrogen. In the complex catalyst represented by the general formula (3), Y ¹ is nitrogen or carbon, preferably nitrogen. Y ² is nitrogen or carbon. In addition, Y ¹ and Y ² are bonded by a single bond or a double bond.

In the complex catalyst represented by the general formula (3) or (4), A ^{1 to} A ⁷ are independently any of oxygen, sulfur, nitrogen, and carbon, preferably nitrogen or carbon. In the complex catalyst represented by the general formula (5), A ^{8 to} A ⁹ are independently either nitrogen or carbon.

In the complex catalyst represented by any of the general formulas (1) to (5), T is a hydrogen atom, an alkyl group, an aromatic group, a hydroxy group (-OH), an alkoxy group (-OR), or an amino. Any substituent such as a group (-NRR'), an amide group, an acyl group, etc.

In the complex catalyst represented by the general formula (1) or (2), L is an aromatic anion ligand or an aromatic ligand, and one substituent or a substituent is placed on this ligand. You may have more than one. The substituent on this ligand may be any, for example, alkyl group, hydroxy group (-OH), ester group (-COOR), amide group (-CONRR'), halogen (-X), Alkoxy group (-OR), alkylthio group (-SR), amino group (-NRR'), acyl group, carboxylic acid group (-COOH), nitro group, sulfonic acid group (-SO ₃ H), aromatic group, etc. When there are a plurality of substituents, they may be the same or different. Particularly preferably, pentamethylcyclopentadienyl or hexamethylbenzene, which are all substituted with methyl groups, is preferable.

In the complex catalyst represented by any of the general formulas (3) to (5), R ^{1 to} R ⁹ independently represent a hydrogen atom, an alkyl group, a hydroxy group, an alkoxy group, an oxyanion group, an oxo group, and a nitro. It is a group, a halogen group, a sulfone group, an acyl group, a carboxylic acid group or a derivative thereof, an amino group, an alkylamino group, an amide group, or a phenyl group, and may have a substituent. If it has a substituent, the substituent may be one or more, and if A ⁱ (i is an integer of 1 to 7) is oxygen or sulfur, R ^{i at} that position is present. In the case of nitrogen, it is possible to have a maximum of one substituent, and in the case of carbon, a maximum of two substituents bonded by a single bond or one substituent bonded by a double bond. It is also possible to have.) Desirably, it is a hydrogen atom, a hydroxy group, an oxo group, or an alkoxy group.

In the present invention, the alkyl group is not particularly limited, but for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and the like. Pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecil group, icosyl group and the like. Be done. The same applies to groups derived from alkyl groups, such as hydroxyalkyl groups, alkoxyalkyl groups, dialkylaminoalkyl groups, and atomic groups (alkoxy groups, etc.). The same applies to the alkyl groups constituting the carboxylic acid ester group and the carboxylic acid alkyl amide group. The alcohol and alkoxide ion are not particularly limited, and examples thereof include alcohol and alkoxide ion derived from each of the alkyl groups. Further, in the present invention, "halogen" refers to any halogen element, and examples thereof include fluorine, chlorine, bromine, and iodine. Further, when an isomer is present in the substituent or the like in the present invention, any isomer may be used unless otherwise specified. For example, the term "propyl group" may be either an n-propyl group or an isopropyl group. The term "butyl group" may be any of an n-butyl group, an isobutyl group, a sec-butyl group and a tert-butyl group. However, this description is merely an example of a possible mechanism and does not limit the present invention.

The complex catalyst of the present invention contains a metal complex represented by any of the general formulas (1) to (5), a homozygous or stereoisomer thereof, or a salt thereof as an active ingredient, and hydrogen of carbon dioxide. It is a catalyst for producing formic acid and / or formate by hydrogenation. The active ingredient of the catalyst is at least one selected from the group consisting of metal complexes represented by any of the general formulas (1) to (5), tautomers thereof, steric isomers, and salts thereof. Consists of compounds. For example, one or more kinds of ligands of the ligand component may be mixed with the metal component of any one of the general formulas (1) to (5) to be an active ingredient, or the ligand component may be used from the beginning. And the metal component may be mixed to synthesize and isolate the active ingredient for use. Further, other components may be added as appropriate (preferably less than 10 wt%) for use.

The complex catalyst of the present invention may be prepared before the hydrogenation reaction of carbon dioxide, and the prepared complex catalyst may be added to the reaction solution for reaction, or the metal salt portion and the ligand portion are mixed and the complex catalyst is used. The hydrogenation reaction of carbon dioxide may be started as it is without separating and purifying.

The ligand constituting the complex catalyst of the present invention has an amide (thioamide) structure. It has been found that amide nitrogen exhibits a strong electron donating property by deprotonating when coordinating with a metal to generate a negative charge in the molecule, and as a result, activates a catalyst ([Chemical Formula 8]). On the other hand, in the carboxylic acid group that is also deprotonated, no significant catalytic activation is observed due to the oxygen atom having a high electronegativity. In addition, the amidine group showed only limited catalytic activity because deprotonation was unlikely to occur. This time, we were able to find a new catalyst with high activity by coordinating an amide group that deprotonates during coordination.

Furthermore, further activation of the catalyst of the present invention can be achieved by well known methods. That is, in the complex catalyst represented by the general formula (4) or (5), by introducing a hydroxyl group into the 5-membered ring or the 6-membered ring, an oxyanion is generated under the hydrogenation reaction condition of carbon dioxide, and the coordination is performed. It is possible to enhance the electron donating property on the child and further improve the catalytic performance. For example, in the case of the picoline amide ligand having a hydroxyl group shown in [Chemical formula 9], the catalytic activity is further improved by deprotonating the hydroxyl group to generate a negative charge on the pyridine ring under carbon dioxide hydrogenation reaction conditions. At that time, the hydroxypyridine ligand may form a pyridone skeleton.

The method for hydrogenating carbon dioxide (or the method for producing formic acid and / or formate) of the present invention is a method for producing a catalyst containing the metal complex of the present invention, a homovariant or stereoisomer thereof, or a salt thereof as an active ingredient. It comprises at least one step selected from the group consisting of a step of stirring the solution in the presence of carbon dioxide and hydrogen, and a step of heating the solution. That is, for example, the solution of the complex catalyst represented by any of the general formulas (1) to (5) may be allowed to stand or stirred as it is in the presence of carbon dioxide and hydrogen, or may be heated if necessary.

In the method for hydrogenating carbon dioxide (or the method for producing formic acid and / or formate) of the present invention, it is advantageous that the reaction temperature does not decompose the catalyst and the reaction proceeds at a sufficient reaction rate. Generally, the reaction can be carried out in the range of 0 ° C. to 300 ° C., but is preferably in the range of 40 ° C. or higher and 100 ° C. or lower. The reaction time is not particularly limited. The reaction is preferably carried out under conditions of hypoxia or the absence of oxygen, and the reaction medium is preferably used after degassing. Further, the reaction operation is preferably carried out in an atmosphere of an inert gas such as nitrogen or argon.

In the method for hydrogenating carbon dioxide (or the method for producing formate of formic acid and / or formate) of the present invention, there is no upper or lower limit on the amount of the complex catalyst used, but the reaction rate and the complex catalyst in the reaction solution are not limited. Depends on solubility and economic efficiency. Suitable catalyst concentrations are 1 × 10 ^-9 to 1 × 10 ^-1 M, preferably 1 × 10 ^-7 to 1 × 10 ^-4 M.

In the method for hydrogenating carbon dioxide (or the method for producing formic acid and / or formate) of the present invention, the reaction is promoted by using a base. For example, examples of inorganic bases include lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, strontium carbonate, lithium carbonate, lithium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, etc. Potassium hydrogen carbonate, calcium carbonate, barium carbonate, strontium carbonate and the like are suitable. Examples of organic bases include, but are not limited to, ammonia, triethylamine, diisopropylethylamine, aniline, pyridine and the like. Generally, the pH of the reaction solution is used in the range of 4 to 14 (preferably 6 to 9), but it exceeds this range because the pH of the reaction solution changes due to the dissolution of carbon dioxide gas in the reaction solution. Carbon dioxide may be hydrolyzed.

In the method for hydrogenating carbon dioxide (or the method for producing formic acid and / or formate) of the present invention, the pressure used for the reaction is not particularly upper and lower limits, but is generally higher than normal pressure. Higher pressures are preferred, but depend on economic reasons such as equipment and operating costs.

The reaction solvent used in the method for hydrogenating carbon dioxide of the present invention (method for producing formic acid and / or formate) is not particularly limited, and for example, water or an organic solvent may be used, or only one type may be used, or two types may be used. The above may be used together. When the complex catalyst of the present invention is soluble in water, it is preferable to use water because it is easy to use. The organic solvent is not particularly limited, but a highly polar solvent is preferable from the viewpoint of solubility of the complex and the like, and nitriles such as acetonitrile, propionitrile, butyronitrile and benzonitrile, methanol, ethanol, n-propyl alcohol and n-butyl alcohol are preferable. Primary alcohols such as, isopropyl alcohol, secondary alcohols such as s-butyl alcohol, tertiary alcohols such as t-butyl alcohol, polyhydric alcohols such as ethylene glycol and propylene glycol, tetrahydrofuran, dioxane, dimethoxyethane, etc. Examples thereof include ethers such as diethyl ether, amides such as dimethylformamide and dimethylacetamide, sulfoxides such as dimethylsulfoxide, and esters such as ethyl acetate.

Hereinafter, examples of the present invention will be described in more detail, but the present invention is not limited to the following examples.

[Example 1]
[Complex synthesis]
The catalytic ligand (0.08 mmol) and [Cp ^* Ir (H ₂ O) ₃ ] SO ₄ (38.2 mg, 0.08 mmol) were stirred in water at 30 ° C. for 12 hours. The reaction solution was concentrated under reduced pressure, and the obtained product was dried under reduced pressure for 12 hours to obtain a complex catalyst. The analytical values of the synthesized catalyst are shown below.

¹H NMR (D₂O, 400 MHz): δ = 8.76 (ddd, J = 5.50, 1.50, 0.75 Hz, 1H, ArH), 8.05 (td, J = 7.80, 1.45 Hz, 1H, ArH), 7.85 (ddd, J = 6.90, 1.40, 0.75 Hz, 1H, ArH), 7.63 (ddd, J = 7.70, 5.45 1.50 Hz, 1H, ArH) and 1.62 (s, 15H, Cp*). ¹³C NMR (D₂O, 150 MHz): δ = 176.04 (C=O), 153.02 (Ar), 151.89 (Ar), 141.45 (Ar), 129.93 (Ar), 126.11 (Ar), 87.32 (Cp*) and 8.49 (Cp*). ESI-MS (m/z): [M−HSO₄−H₂O]⁺ calcd for C₁₆H₂₀IrN₂O⁺, 449.12; found, 449. Elemental analysis calcd (%) for C₁₆H₂₃IrN₂O₆S: C, 34.10; H, 4.11; N, 4.97. Found: C; 34.04; H, 4.28; N, 5.15. Complex with picolinamide as a ligand (6)

¹ H NMR (D ₂ O, 400 MHz): δ = 8.76 (ddd, J = 5.50, 1.50, 0.75 Hz, 1H, ArH), 8.05 (td, J = 7.80, 1.45 Hz, 1H, ArH), 7.85 ( ddd, J = 6.90, 1.40, 0.75 Hz, 1H, ArH), 7.63 (ddd, J = 7.70, 5.45 1.50 Hz, 1H, ArH) and 1.62 (s, 15H, Cp *). ¹³ C NMR (D ₂ O) , 150 MHz): δ = 176.04 (C = O), 153.02 (Ar), 151.89 (Ar), 141.45 (Ar), 129.93 (Ar), 126.11 (Ar), 87.32 (Cp *) and 8.49 (Cp *) . ESI-MS (m / z): [M−HSO ₄ −H ₂ O] ⁺ calcd for C ₁₆ H ₂₀ IrN ₂ O ⁺ , 449.12; found, 449. Elemental analysis calcd (%) for C ₁₆ H ₂₃ IrN ₂ O ₆ S: C, 34.10; H, 4.11; N, 4.97. Found: C; 34.04; H, 4.28; N, 5.15.

¹H NMR (D₂O, 400 MHz): δ = 8.84 (ddd, J = 5.52, 1.44, 0.72 Hz, 1H, ArH), 8.12 (td, J = 7.80, 1.44 Hz, 1H, ArH), 7.86 (ddd, J = 7.84, 1.44, 0.72 Hz, 1H, ArH), .7.69 (ddd, J = 7.64, 5.56, 1.52 Hz, 1H, ArH), 3.37 (s, 3H, Me) and 1.59 (s, 15H, Cp*). ¹³C NMR (D₂O, 150 MHz): δ = 173.41 (C=O), 153.61 (Ar), 151.36 (Ar), 141.36 (Ar), 129.36 (Ar), 125.69 (Ar), 87.65 (Cp*), 37.26 (Me) and 8.46 (Cp*). ESI-MS (m/z): [M−HSO₄−H₂O]⁺ calcd for C₁₇H₂₂IrN₂O⁺, 463.14; found, 463. Elemental analysis calcd (%) for C₁₇H₂₅IrN₂O₆S: C, 35.35; H, 4.36; N, 4.85. Found: C; 35.07; H, 4.23; N, 4.81.
X線結晶構造解析により、アミド窒素のプロトンが脱離した上記構造であることを確認した。 Complex with N-methylpicolinamide as a ligand (7)

^{1 1} H NMR (D ₂ O, 400 MHz): δ = 8.84 (ddd, J = 5.52, 1.44, 0.72 Hz, 1H, ArH), 8.12 (td, J = 7.80, 1.44 Hz, 1H, ArH), 7.86 ( ddd, J = 7.84, 1.44, 0.72 Hz, 1H, ArH), .7.69 (ddd, J = 7.64, 5.56, 1.52 Hz, 1H, ArH), 3.37 (s, 3H, Me) and 1.59 (s, 15H, Cp *). ¹³ C NMR (D ₂ O, 150 MHz): δ = 173.41 (C = O), 153.61 (Ar), 151.36 (Ar), 141.36 (Ar), 129.36 (Ar), 125.69 (Ar), 87.65 (Cp *), 37.26 (Me) and 8.46 (Cp *). ESI-MS (m / z): [M−HSO ₄ −H ₂ O] ⁺ calcd for C ₁₇ H ₂₂ IrN ₂ O ⁺ , 463.14; found, 463. Elemental analysis calcd (%) for C ₁₇ H ₂₅ IrN ₂ O ₆ S: C, 35.35; H, 4.36; N, 4.85. Found: C; 35.07; H, 4.23; N, 4.81.
By X-ray crystallography, it was confirmed that the structure was such that the protons of amide nitrogen were eliminated.

¹H NMR (D₂O, 400 MHz): δ = 8.56 (d, J = 6.32 Hz, 1H, ArH), 7.27 (d, J = 2.68 Hz, 1H, ArH), 7.08 (dd, J = 6.36, 2.84 Hz, 1H, ArH) and 1.62 (s, 15H, Cp*). ¹³C NMR (D₂O, 150 MHz): δ = 176.10 (C=O), 167.43 (Ar), 154.66 (Ar), 152.67 (Ar), 116.58 (Ar), 113.92 (Ar), 86.77 (Cp*), and 8.51 (Cp*). ESI-MS (m/z): [M−HSO₄−H₂O]⁺ calcd for C₁₆H₂₀IrN₂O₂ ⁺, 465.12; found, 465. Elemental analysis calcd (%) for C₁₆H₂₃IrN₂O₇S+H₂O: C, 32.15; H, 4.22; N, 4.69. Found: C; 31.86; H, 3.95; N, 4.63. Complex with 4-hydoxypicolinamide as a ligand (8)

^{1 1} H NMR (D ₂ O, 400 MHz): δ = 8.56 (d, J = 6.32 Hz, 1H, ArH), 7.27 (d, J = 2.68 Hz, 1H, ArH), 7.08 (dd, J = 6.36, 2.84 Hz, 1H, ArH) and 1.62 (s, 15H, Cp *). ¹³ C NMR (D ₂ O, 150 MHz): δ = 176.10 (C = O), 167.43 (Ar), 154.66 (Ar), 152.67 (Ar), 116.58 (Ar), 113.92 (Ar), 86.77 (Cp *), and 8.51 (Cp *). ESI-MS (m / z): [M−HSO ₄ −H ₂ O] ⁺ calcd for C ₁₆ H ₂₀ IrN ₂ O ₂ ⁺ , 465.12; found, 465. Elemental analysis calcd (%) for C ₁₆ H ₂₃ IrN ₂ O ₇ S + H ₂ O: C, 32.15; H, 4.22; N, 4.69. Found: C; 31.86; H, 3.95; N, 4.63.

¹H NMR (D₂O, 400 MHz): δ = 8.60 (d, J = 6.35 Hz, 1H, ArH), 7.32 (d, J = 2.85 Hz, 1H, ArH), 7.14 (dd, J = 6.35, 2.80 Hz, 1H, ArH), 3.43 (s, 3H, Me) and 1.66 (s, 15H, Cp*). ¹³C NMR (D₂O, 150 MHz): δ = 173.43 (C=O), 167.36 (Ar), 155.33 (Ar), 151.96 (Ar), 115.99 (Ar), 113.34 (Ar), 87.14 (Cp*), 37.31 (Me) and 8.49 (Cp*). ESI-MS (m/z): [M−HSO₄−H₂O]⁺ calcd for C₁₇H₂₂IrN₂O₂ ⁺, 479.13; found, 479. Elemental analysis calcd (%) for C₁₇H₂₅IrN₂O₇S: C, 34.39; H, 4.24; N, 4.72. Found: C; 34.33; H, 4.16; N, 4.67. Complex with 4-hydoxy-N-methylpyroline amide as a ligand (9)

^{1 1} H NMR (D ₂ O, 400 MHz): δ = 8.60 (d, J = 6.35 Hz, 1H, ArH), 7.32 (d, J = 2.85 Hz, 1H, ArH), 7.14 (dd, J = 6.35, 2.80 Hz, 1H, ArH), 3.43 (s, 3H, Me) and 1.66 (s, 15H, Cp *). ¹³ C NMR (D ₂ O, 150 MHz): δ = 173.43 (C = O), 167.36 ( Ar), 155.33 (Ar), 151.96 (Ar), 115.99 (Ar), 113.34 (Ar), 87.14 (Cp *), 37.31 (Me) and 8.49 (Cp *). ESI-MS (m / z): [ M−HSO ₄ −H ₂ O] ⁺ calcd for C ₁₇ H ₂₂ IrN ₂ O ₂ ⁺ , 479.13; found, 479. Elemental analysis calcd (%) for C ₁₇ H ₂₅ IrN ₂ O ₇ S: C, 34.39; H , 4.24; N, 4.72. Found: C; 34.33; H, 4.16; N, 4.67.

Complex catalysts with the following ligands, with the corresponding catalytic ligands, [Cp ^* Ir (H ₂ O) ₃ ] SO ₄ , [(C ₆ Me ₆ ) Ru (H ₂ O) ₃ ] SO ₄ , [Cp ^* Rh (H ₂ O) ₃ ] SO ₄ was prepared by reacting in water.

[Example 2]
From the solution prepared in Example 1 in which 8.0 μmol of the complex catalyst was dissolved in water (1 mL), 25 μL (0.2 μmol) was added to a degassed 1 M aqueous sodium hydrogen carbonate solution (10 mL), and hydrogen at 50 ° C. and 1 MPa was added. : The mixture was vigorously stirred under the pressure of carbon dioxide (1: 1). After 1 hour, the formic acid concentration of the reaction solution was used in high performance liquid chromatography ^{and passed through a column (TSKgel SCX (H +} ): TOSOH) containing a 20 mM hydrogen phosphate solution as the developing solution, and the flowing solution was passed at a wavelength of 210 nm. The measurement results are shown in Table 1.

[Example 3]
The complex catalyst (9) (0.2 μmol) produced in Example 1 was added to a 1 M aqueous sodium hydrogen carbonate solution (20 mL), and violently in an atmosphere of hydrogen: carbon dioxide (1: 1) at 25 ° C. and atmospheric pressure. Stirred. The formic acid concentration of the reaction solution taken out at appropriate intervals was measured, and the catalyst rotation speed and the formic acid concentration are shown in FIG. As a result, the hydrogenation reaction of carbon dioxide under normal temperature and pressure conditions in water showed extremely high catalytic activity with a catalyst rotation speed (catalyst rotation efficiency) of 167 times per hour and a catalyst rotation speed of 14700 times after 2 weeks.

[Comparative Example 1]
A formate produced by the hydrogenation reaction of carbon dioxide under the same reaction conditions of hydrogen at 50 ° C. and 1 MPa using a complex catalyst represented by the formula (23) as a bipyridine ligand: carbon dioxide (1: 1). The catalyst rotation speed of was 1 time. These results are less than those of the complex catalysts (6) to (21) using the amide moiety as a ligand, indicating that the catalyst liganded with amide nitrogen is effective for the hydrogenation reaction of carbon dioxide. There is.

The complex catalyst of the present invention is effective for the production of formic acid and / or formate by hydrogenation of carbon dioxide (the production is also a storage of hydrogen because hydrogen can be extracted from formic acid and / or formate). Is. Moreover, since the catalyst structure is relatively simple, not only can it be prepared inexpensively, but it can also be changed to various derivatives. Therefore, by using the complex catalyst found in the present invention, formic acid and / or formate, which can be easily stored and transported, can be energy-efficiently produced from carbon dioxide and hydrogen. Further, as an effective utilization technology of carbon dioxide, it is also possible to convert carbon dioxide into a formic acid derivative or a further useful carbon compound such as methanol by using carbon dioxide as a C1 raw material. In this case, it is not necessary to prepare and separate the complex catalyst to be used in advance, and it can be used as a catalyst simply by mixing the ligand component and the metal component in advance, so that it can be incorporated into a carbon dioxide hydrogenation reactor. It's easy.

Claims (9)

Is represented by the general formula (1), coordination metal complexes by X ¹ and nitrogen bidentate ligand ^{(X 1 -X 2 -C (=} Z) -NT) (N), an isomer thereof, or a salt A catalyst for producing formic acid and / or formate by hydrogenation of carbon dioxide, which comprises as an active ingredient.

In the general formula (1)
M is, iridium, rhodium or ruthenium-time,
L is an aromatic anion ligand or an aromatic ligand, and when it has a substituent, the substituent may be one or more.
J is any ligand or does not exist,
X ⁱ (i is 1 or 2) is any of nitrogen, oxygen, sulfur, and carbon, and when X ⁱ is nitrogen, it may have a substituent Q ⁱ bonded in a single bond, and X ⁱ If is carbon, it may have a substituent Q ⁱ bonded by a single bond or a double bond.
X ¹ and X ² are single-bonded or double-bonded,
When Q ⁱ (i is 1 or 2) is ^{bonded to X i} by a single bond, hydrogen atom, alkyl group, hydroxy group, alkoxy group, oxyanion group, oxo group, nitro group, halogen group, sulfone group, acyl A group, a carboxylic acid group or a derivative thereof, an amino group, an alkylamino group, an amide group, or a phenyl group, where X ⁱ is a carbon and Q ⁱ is bonded by a ^{X i} single bond, up to two ^{Q i can exist.} When Q ⁱ is double-bonded to X ^{i , Q i} is oxygen (= O), sulfur (= S), nitrogen (= NR), or carbon (= CRR'), and nitrogen, Alternatively, in the case of carbon, it may have a substituent (R or R').
Q ¹ and Q ² may be bonded through a substituent to form a ring.
Z is either oxygen or sulfur,
T is a hydrogen atom, or any substituent
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer. A metal complex having a bidentate ligand having a ring structure, coordinated with ^{Y 1 of Y 1} -Y ^2- C (= O) -NT, represented by the general formula (2), and an isomer thereof. Or a catalyst for producing formic acid and / or formate by hydrogenation of carbon dioxide, which contains a salt as an active ingredient.

In the general formula (2)
M is, iridium, rhodium, is any of ruthenium-time,
L is an aromatic anion ligand or an aromatic ligand, and when it has a substituent, the substituent may be one or more.
J is any ligand or does not exist,
Y ¹ is either nitrogen, oxygen, sulfur or carbon,
Y ² is nitrogen or carbon,
Y ¹ and Y ² may be single or double bonded and may have a substituent on the ring between ^{Y 1} and Y ^2.
T is a hydrogen atom, or any substituent,
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer. The formic acid and / or formate by hydrogenation of carbon dioxide according to claim 1 or 2, wherein M in the general formula (1) or (2) is iridium and L is a pentamethylcyclopentadienyl ligand. A catalyst for manufacturing. Hydrogenation of carbon dioxide represented by the general formula (3) and containing a metal complex having a bidentate ligand coordinated with amide nitrogen and nitrogen or carbon on a 6-membered ring, an isomer thereof, or a salt as an active ingredient. A catalyst for producing formic acid and / or formate by hydrogenation.

In the general formula (3)
J is any ligand or does not exist,
Y ¹ is a nitrogen or carbon-containing,
Y ² is nitrogen or carbon,
A ^{1 to} A ⁴ are independently one of oxygen, sulfur, nitrogen, and carbon.
Each atom of the 6-membered ring consisting of Y ¹ , Y ² and A ^{1 to} A ⁴ forms a single bond, a double bond, or an aromatic ring.
R ^{1 to} R ⁴ are independently hydrogen atom, alkyl group, hydroxy group, alkoxy group, oxyanion group, oxo group, nitro group, halogen group, sulfone group, acyl group, carboxylic acid group or derivative thereof, amino. It may be a group, an alkylamino group, an amide group, or a phenyl group and may have a substituent, and when it has a substituent, the substituent may be one or more (however, A). ^{If i} (i is an integer of 1 to 4) is oxygen or sulfur, then R ^{i at} that position does not exist, and if A ⁱ is nitrogen, it is possible to have ^{up to one substituent R i, A. If i} is carbon, it is ^{also possible to have up to two substituents R i} or one substituent bonded by a double bond.)
T is a hydrogen atom, or any substituent,
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer. Formic acid and / or formic acid by hydrogenation of carbon dioxide, which is represented by the general formula (4) and contains a metal complex having a bidentate ligand consisting of amide nitrogen and a 5-membered ring, an isomer thereof, or a salt as an active ingredient. A catalyst for producing salt.

In the general formula (4)
J is any ligand or does not exist,
Y ¹ is either nitrogen, oxygen, sulfur or carbon,
Y ² is nitrogen or carbon,
A ^{5 to} A ⁷ are independently one of oxygen, sulfur, nitrogen, and carbon.
Each atom of the 5-membered ring consisting of Y ¹ , Y ² and A ^{5 to} A ⁷ is single-bonded, double-bonded, or forms an aromatic ring.
R ^{5 to} R ⁷ are independently hydrogen atom, alkyl group, hydroxy group, alkoxy group, oxyanion group, oxo group, nitro group, halogen group, sulfone group, acyl group, carboxylic acid group or derivative thereof, amino. It may be a group, an alkylamino group, an amide group, or a phenyl group and may have a substituent, and when it has a substituent, the substituent may be one or more (however, A). ^{If i} (i is an integer of 5-7) is oxygen or sulfur, then R ^{i at} that position does not exist, and if A ⁱ is nitrogen, it is possible to have ^{up to one substituent R i.} If A ⁱ is carbon, it is ^{also possible to have up to two substituents R i} or one substituent bonded by a double bond.)
T is a hydrogen atom, or any substituent,
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer. Carbon dioxide represented by the general formula (5) and containing, as an active ingredient, a metal complex having a bidentate ligand coordinated with amide nitrogen and nitrogen on a 6-membered aromatic nitrogen-containing ring, an isomer thereof, or a salt thereof. A catalyst for producing formate and / or formate by hydrogenation of.

In the general formula (5)
J is any ligand or does not exist,
T is a hydrogen atom, or any substituent
A ⁸ and A ⁹ are independently nitrogen or carbon, respectively.
R ⁸ and R ⁹ are independently hydrogen atom, alkyl group, hydroxy group, alkoxy group, oxyanion group, nitro group, halogen group, sulfone group, acyl group, carboxylic acid group or derivative thereof, amino group, alkyl. An amino group, an amide group, or a phenyl group with or without a substituent,
n represents the charge of the metal complex and is a positive integer, 0, or a negative integer. In any of the general formulas (1) to (5), J is a water molecule, a hydrogen atom, an alkoxide ion, a hydroxide ion, a halide ion, a carbonate ion, a trifluoromethanesulfonic acid ion, a sulfate ion, and a hydrogen sulfate ion. , Nitrate ion, formate ion, or acetate ion, or a catalyst for producing formate and / or formate by hydrogenation of carbon dioxide according to any one of claims 1 to 6, which is not present. A method for hydrogenating carbon dioxide to produce formic acid and / or formate by reacting hydrogen with carbon dioxide in the presence of the catalyst according to any one of claims 1 to 7. A method for storing hydrogen by reacting hydrogen with carbon dioxide in the presence of the catalyst according to any one of claims 1 to 7 to produce formic acid and / or formate.

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