JP2010195703A - New molybdenum complex - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new compound employable as a catalyst for synthesizing ammonia from nitrogen without requiring formation of hydrogen and to provide a production method and a use method of such an ammonia synthesis catalyst and an intermediate compound used for the production of such an ammonia synthesis catalyst. <P>SOLUTION: For example, a molybdenum complex of a structure represented by formula (II) is exemplified. In the formula,<SP>i</SP>Pr denotes i-propyl; Me denotes methyl; and Ph denotes phenyl. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a novel molybdenum complex. In particular, the present invention relates to a novel molybdenum complex that can be used as an ammonia synthesis catalyst for synthesizing ammonia without going through hydrogen. The present invention also relates to methods for producing and using such complexes, and intermediates.

The chemical synthesis of ammonia was first successful in mass production about 100 years ago by German researchers Haber and Bosch. The Harbor-Bosch synthesis method is a reaction represented by the following formula, and is simple and relatively high in efficiency. Therefore, it is still used basically without change:
N ₂ + 3H ₂ → 3NH ₃ (about 400 ° C.)

Conventionally, hydrogen for the synthesis of ammonia has been obtained using natural gas mainly composed of methane (CH ₄ ). It has also been proposed to obtain hydrogen for the synthesis of ammonia by electrolysis of water. However, in either case, a large amount of energy is required to generate hydrogen.

  Therefore, it has been studied to synthesize ammonia without going through production of hydrogen. For example, in Non-Patent Document 1, a tungsten or molybdenum dinitrogen complex having 1,1′-bis (diethylphosphino) ferrocene as an auxiliary functional group is reacted with an excess amount of sulfuric acid in methanol at room temperature. Proposed to produce ammonia.

Masahiro Yuki, Yoshihiro Miyake and Yoshiaki Nishibayashi, Organometallics, 2008, 27 (15), pp3947-3953 "Synthesis and Reactivity of Tungsten-and Molybdenum-Dinitrogen Complexes Bearing Ferrocenyldiphosphines toward Protonolysis"

  As described above, it has been studied to synthesize ammonia without going through the production of hydrogen. Therefore, the present invention provides a novel complex that can be used as a catalyst for synthesizing ammonia from nitrogen without going through hydrogen generation. The present invention also provides methods for producing, using, and intermediates for such complexes.

  The present invention has been made by discovering that specific molybdenum complexes can synthesize ammonia from nitrogen without going through the production of hydrogen, and the present invention provides such a molybdenum complex, a method for producing the same, and the like. And a method for producing the same, and a method for producing hydrogen using such a molybdenum complex.

  According to the present invention, ammonia can be effectively synthesized from nitrogen without using hydrogen generation by using the molybdenum complex of the present invention as a catalyst.

<< First Molybdenum Complex (Catalyst) of the Present Invention >>
The first molybdenum complex of the present invention can be used as a catalyst for synthesizing ammonia from nitrogen without going through hydrogen generation, and has the following formula (I):

In the above formula (I), R _{1 to} R ₄ are each independently selected from the group consisting of hydrogen and a C _{1 to} C ₁₄ chain, cyclic or branched hydrocarbon group. Here, R ₁ and R ₂ and / or R ₃ and R ₄ may be bonded to each other to form a ring. Moreover, PR ₁ R ₂ and PR ₃ R ₄ may be the same or different. Furthermore, R _{1 to} R ₄ may all be the same or at least partially different.

In the above formula (I), R _a is _{a group} that optionally substitutes 1 to 3 hydrogens of the aromatic ring, and consists of a C ₁ -C ₁₄ chain, cyclic or branched hydrocarbon group. Selected from the group. Here, R _a is absent, the aromatic ring may be unsubstituted. Further, when two or three R _a are present, these R _a may be bonded to each other to form a ring. Furthermore, when two or three R _a are present, these may be all the same or at least partially different.

In the above formula (I), L ₁ is selected from the group consisting of a ligand having phosphorus as a coordination moiety, a ligand having nitrogen as a coordination moiety, and a ligand having dinitrogen as a coordination moiety. Is done.

  Specifically, the first molybdenum complex of the present invention can have any of the following formulas (II) to (IV):

(In formulas (II) to (IV), ⁱ Pr represents i-propyl, Me represents methyl, and Ph represents phenyl).

<< Method for Producing the First Molybdenum Complex (Catalyst) of the Present Invention >>
The first molybdenum complex of the present invention having the above formulas (I) to (IV) is obtained by converting three of the ligands L _{1 to} L ₄ of the molybdenum complex having the following formula (V) into the following formula: It can be prepared by a process comprising substitution with a pincer ligand having (VI):

(L _{1 to} L ₄ are each independently selected from the group consisting of a ligand having phosphorus as a coordination moiety, a ligand having nitrogen as a coordination moiety, and a ligand having dinitrogen as a coordination moiety. );

(R ₁ -R ₄ and R _a are as described above with respect to formula (I)).

<< Second Molybdenum Complex (Precursor) of the Present Invention >>
The second molybdenum complex of the present invention can be used as a precursor of the first molybdenum complex of the present invention and has the following formula (VII):

(R ₁ -R ₄ and R _a are as described above with respect to formula (I), and X ₁ -X ₃ are each independently selected from the group consisting of fluorine, chlorine, bromine and iodine).

<< Method for Producing Second Molybdenum Complex (Precursor) of the Present Invention >>
The second molybdenum complex of the present invention includes replacing the ligands Y _{1 to} Y ₃ of the molybdenum complex having the following formula (VIII) with a pincer-type ligand having the following formula (VI). Can be produced by the method:

(X _{1 to} X ₃ are each independently selected from the group consisting of fluorine, chlorine, bromine and iodine, and Y _{1 to} Y ₃ are each independently a ligand that can be substituted by a pincer ligand, such as tetrahydrofuran. );

(R ₁ -R ₄ and R _a are as described above with respect to formula (I)).

<< Method for Producing the First Molybdenum Complex (Catalyst) of the Present Invention from the Second Molybdenum Complex (Precursor) of the Present Invention >>
The first molybdenum complex of the present invention is produced by a method comprising substituting two of the ligands X _{1 to} X ₃ of the second molybdenum complex of the present invention with a dinitrogen ligand. Can do.

<< Synthesis of silylamine and / or ammonia >>
In the method of the present invention for producing silylamine, silylamine is produced from silyl chloride by the reaction represented by the following formula using the first molybdenum complex of any one of the above formulas (I) to (IV) as a catalyst. Including:
_{SiR p R q R r Cl +} 1 / 2N 2 + Na
→ N (SiR _p R _q R _r ) ₃ + NaCl

In this reaction, R _p , R _q and R _r are each independently selected from the group consisting of hydrogen and a C ₁ -C ₁₄ chain, cyclic or branched hydrocarbon group. Here, two or three of R _p , R _q and R _r may be bonded to each other to form a ring. R _p , R _q and R _r may all be the same or at least partially different.

  This method for producing silylamine can be carried out in a non-aqueous solvent such as tetrahydrofuran in a nitrogen atmosphere under mild conditions, for example at room temperature.

Also, the method of the present invention for producing ammonia comprises obtaining silylamine as in the method of the present invention for producing silylamine, and hydrolyzing the silylamine thus obtained by a reaction represented by the following formula: including:
_{N (SiR p R q R r} ) 3 + 3H 2 O
→ 3SiR _p R _q R _r (OH) + NH ₃
(R _p , R _q and R _r are as described above).

  This method of producing ammonia can be performed, for example, by adding an excess of sulfuric acid and water to the silylamine.

Definition
In the present invention, the “ligand having phosphorus as a coordination moiety” is, for example, a ligand represented by the formula PR ₅ R ₆ R ₇ , and R ₅ , R ₆ , and R ₇ are each independently hydrogen , And C ₁ -C ₁₄ chain, cyclic or branched hydrocarbon groups. Here, two or three of R ₅ , R ₆ and R ₇ may be bonded to each other to form a ring. R _{5 to} R ₇ may all be the same or at least partially different.

Thus, for example, ligands represented by “PR ₅ R ₆ R ₇ ” include tertiary phosphines such as trialkylphosphine such as trimethylphosphine, triarylphosphine such as triphenylphosphine, and methyldiphenylphosphine. And alkylaryl phosphines such as dimethylphenylphosphine can be selected.

In the present invention, the “ligand having nitrogen as a coordination moiety” is, for example, a ligand represented by the formula NR ₈ R ₉ , wherein R ₈ and R ₉ are each independently hydrogen, C ₁ -C ₁₄ chain is selected from the group consisting of cyclic or branched hydrocarbon group. Here, R ₈ and R ₉ may be bonded to each other to form a ring. R ₈ and R ₉ may be the same or different.

Therefore, for example, as the ligand represented by “NR ₈ R ₉ ”, a nitrogen-containing aromatic such as aniline can be selected.

In the present invention, the “ligand having dinitrogen as a coordination moiety” is, for example, a ligand represented by the formula NNR ₁₀ , wherein R ₁₀ is a bond, hydrogen, and C _{1 to} C ₁₄ . It is selected from the group consisting of chain, cyclic or branched hydrocarbon groups.

Thus, for example, dinitrogen (NN, ie, R ₁₀ is a bond) can be selected as the ligand represented by “NNR ₁₀ ”, and the complex forms a dimer via this dinitrogen. It may be.

In the present invention, the “C ₁ -C ₁₄ chain, cyclic or branched hydrocarbon group” is not limited, but is a C ₁ -C ₆ alkyl group, a C ₂ -C ₆ alkenyl group. , _C 2 -C ₆ alkynyl _group, C 2 -C ₆ alkynyl _group, C 3 -C cycloalkyl group _6, C 3 -C cycloalkenyl group _6, cycloalkynyl group C 3 -C ₆ and, It can be selected from the group consisting of C ₆ -C ₁₄ aryl groups.

In the present invention, the “C ₁ -C ₆ alkyl group” is not limited, but methyl, ethyl, propyl, i-propyl, butyl, t-butyl, i-butyl, pentyl, isopentyl, hexyl, An isohexyl etc. can be mentioned.

In the present invention, the “C ₂ -C ₆ alkenyl group” is not limited, but vinyl, 1-propenyl, 2-propenyl, allyl, i-propenyl, 1,3-butadienyl, 1-butenyl, Examples include pentenyl and hexenyl.

In the present invention, examples of the “C ₂ -C ₆ alkynyl group” include, but are not limited to, 1-propynyl, 2-propynyl, 1-butynyl, 2-butynyl, 1-pentynyl, 2-pentynyl and the like. be able to.

In the present invention, examples of the “C ₃ -C ₆ cycloalkyl group” include, but are not limited to, substituted or unsubstituted cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like.

In the present invention, examples of the “C ₃ -C ₆ cycloalkenyl group” include, but are not limited to, substituted or unsubstituted cyclopropienyl, cyclobutadienyl, cyclopentadienyl, cyclohexenyl and the like. Can do.

In the present invention, examples of the “C ₃ -C ₆ cycloalkynyl group” include, but are not limited to, substituted or unsubstituted cyclopropynyl, cyclobutynyl, cyclopentynyl, cyclohexynyl and the like.

In the present invention, examples of the “C ₆ -C ₁₄ aryl group” include, but are not limited to, substituted or unsubstituted phenyl, naphthyl, anthracenyl, phenanthrenyl and the like.

Example 1 First Molybdenum Complex (Catalyst) of the Present Invention (trans- [Mo (N ₂ ) ₂ (PMePh ₂ ) ( ⁱ PrPNP)] ( ⁱ PrPNP = 2,6-bis (di-iso-propylphosphine) Synthesis of Finomethyl) pyridine)) In a nitrogen atmosphere, 50 mL Schlenk was subjected to molybdenum nitrogen complex trans- [Mo (N ₂ ) ₂ (PMePh ₂ ) ₄ ] (260.1 mg, 0.273 mmol, IR (KBr, cm ^{−1). ):} 1932cm -1 to _{(V NN))} was added, was dissolved in tetrahydrofuran ^{(THF) (20mL), i} PrPNP (126.9mg a pincer ligand, 0.374 mmol) at 50 ° C. by adding Stir for 1 day. The resulting dark purple solution was distilled off under vacuum and then washed with diethyl ether to give the title molybdenum complex a purple solid (65.6 mg, 0.095 mmol, 35% yield). As obtained. The overall reaction of this synthesis is as shown below:

  The analytical results for the product are shown below:

³¹ P { ¹ H} NMR (C ₆ D ₆ ): δ 72.4 (d, ² J _PP = 5.5 Hz, ⁱ PrPNP, 2P), 41.6 (t, ² J _PP = 5.5 Hz, PMePh ₂ , 1P).
¹ H NMR (C ₆ D ₆ ): δ 7.89-7.83 (m, 4H), 7.25-7.18 (m, 4H), 7.09-7.03 (m, 2H), _{^{6.82-6.69 (m, 3H), 3.13-3.11}} (m, C H 2 P i Pr 2, 4H), 2.33 (d, 2 J PH = 4.9Hz, P Me _{Ph 2, 3H), 2.00-1.85 (} m, C H Me 2, 4H), 1.13-1.05 (m, CH Me 2, 12H), 0.92-0.85 (m , CH Me ₂ , 12H).
IR (KBr): 1912 cm ⁻¹ (v _N≡N ).

Example 2 Synthesis of Second Molybdenum Complex (Precursor) of the Present Invention ([MoCl ₃ ( ^t BuPNP)] ( ^t BuPNP = 2,6-bis (di-tert-butylphosphinomethyl) pyridine) Nitrogen Atmosphere Then, molybdenum complex [MoCl ₃ (thf) ₃ ] (56.3 mg, 0.134 mmol) and ⁱ BuPNP (60.2 mg, 0.152 mmol) were added to 20 mL Schlenk, and THF (5 mL) was added at 50 ° C. After the reaction, the solvent is distilled off under vacuum to obtain a tan solid, which is extracted with methylene chloride (4 mL), and hexane is slowly added to the extract to form two layers. The orange crystals obtained by recrystallization are vacuum dried to give the title molybdenum complex a brown solid (66.0 mg, 0.110 mmol, yield 8). %) Is obtained as the total reaction of the synthesis is as shown below.:

In the above reaction formula, ^t Bu is a t-butyl group and thf is tetrahydrofuran.

  The steric structure and crystallographic data of the title molybdenum complex are shown below.

Example 3: Synthesis of the first molybdenum complex (catalyst) of the present invention using the second molybdenum complex (precursor) of the present invention The precursor of the second molybdenum complex of the present invention obtained in Example 2 To synthesize the first molybdenum complex of the present invention. In this synthesis, the molybdenum complex obtained in Example 2 is mixed with 6 equivalents of Na-Hg amalgam and excess pyridine in tetrahydrofuran solvent and stirred overnight at room temperature to give the complex of the invention. Was synthesized. The overall reaction of this synthesis is as shown below.

Example 4 Synthesis of Ammonia with the First Molybdenum Complex of the Present Invention In an atmospheric pressure nitrogen atmosphere, the catalyst amount (0.015 mmol) of the molybdenum complex obtained in Example 1 was added in an excess amount in 40 mL of tetrahydrofuran. Mixed with sodium (60 mmol) and trimethylsilyl chloride (60 mmol) at room temperature. It was confirmed that trimethylsilylamine was produced from trimethylsilyl chloride by the reaction shown below:
_{Si (CH 3) 3 Cl +} 1 / 2N 2 + Na
→ N (Si (CH ₃ ) ₃ ) ₃ + NaCl

Further, water was added to the trimethylsilylamine obtained as described above, and it was confirmed that trimethylsilylamine was hydrolyzed by the following reaction to produce ammonia:
N (Si (CH ₃ ) ₃ ) ₃ + 3H ₂ O
→ 3Si (CH ₃ ) ₃ (OH) + NH ₃

Claims (8)

Molybdenum complex having the following formula (I):

(R _{1 to} R ₄ are each independently selected from the group consisting of hydrogen and a C _{1 to} C ₁₄ chain, cyclic or branched hydrocarbon group;
R _a is a group optionally replacing 1 to 3 hydrogens of an aromatic ring, selected from the group consisting of C _{1 to} C ₁₄ chain, cyclic or branched hydrocarbon groups, and L ₁ is selected from the group consisting of a ligand having phosphorus as a coordination moiety, a ligand having nitrogen as a coordination moiety, and a ligand having dinitrogen as a coordination moiety. The molybdenum complex according to claim 1, having any of the following formulas (II) to (IV):

( ^I Pr represents i-propyl, Me represents methyl, and Ph represents phenyl). Substitution of three of the ligands L _{1 to} L ₄ of the molybdenum complex having the following formula (V) with a pincer ligand having the following formula (VI): Method for producing molybdenum complex according to 2:

(L _{1 to} L ₄ are each independently selected from the group consisting of a ligand having phosphorus as a coordination moiety, a ligand having nitrogen as a coordination moiety, and a ligand having dinitrogen as a coordination moiety. );

(R _{1 to} R ₄ are each independently selected from the group consisting of hydrogen and a C _{1 to} C ₁₄ chain, cyclic or branched hydrocarbon group, and R _a is optionally selected from 1 to A group substituting for three hydrogens and selected from the group consisting of C ₁ -C ₁₄ chain, cyclic or branched hydrocarbon groups). Molybdenum complex having the following formula (VII):

(R _{1 to} R ₄ are each independently selected from the group consisting of hydrogen and a C _{1 to} C ₁₄ chain, cyclic or branched hydrocarbon group;
R _a is a group optionally replacing 1 to 3 hydrogens of an aromatic ring, selected from the group consisting of C _{1 to} C ₁₄ chain, cyclic or branched hydrocarbon groups, and X _{1 to} X ₃ are each independently selected from the group consisting of fluorine, chlorine, bromine and iodine). 5. The molybdenum complex of claim 4, comprising replacing the ligands Y _{1 to} Y ₃ of the molybdenum complex having the following formula (VIII) with a pincer-type ligand having the following formula (VI): Production method:

(X _{1 to} X ₃ are each independently selected from the group consisting of fluorine, chlorine, bromine and iodine, and Y _{1 to} Y ₃ are each independently a ligand that can be substituted by the pincer-type ligand. );

(R _{1 to} R ₄ are each independently selected from the group consisting of hydrogen and a C _{1 to} C ₁₄ chain, cyclic or branched hydrocarbon group, and R _a is optionally selected from 1 to A group substituting for three hydrogens and selected from the group consisting of C ₁ -C ₁₄ chain, cyclic or branched hydrocarbon groups). The method for producing a molybdenum complex according to claim 1 or 2, comprising substituting two of the ligands X _{1 to} X ₃ of the molybdenum complex according to claim 4 with a dinitrogen ligand. . A method for producing silylamine, comprising producing silylamine from silyl chloride by the reaction shown below using the molybdenum complex according to claim 1 or 2 as a catalyst:
_{SiR p R q R r Cl +} 1 / 2N 2 + Na
→ N (SiR _p R _q R _r ) ₃ + NaCl
(R _p , R _q and R _r are each independently selected from the group consisting of hydrogen and a C ₁ -C ₁₄ chain, cyclic or branched hydrocarbon group). A method for synthesizing ammonia comprising obtaining a silylamine by the method of claim 7 and hydrolyzing the silylamine thus obtained by a reaction represented by the following formula:
_{N (SiR p R q R r} ) 3 + 3H 2 O
→ 3SiR _p R _q R _r (OH) + NH ₃
(R _p , R _q and R _r are each independently selected from the group consisting of hydrogen and a C ₁ -C ₁₄ chain, cyclic or branched hydrocarbon group).