JP2003146966A - Metal complex for catalyst precursor for dehydrogenation reaction of organic compound taking advantage of oxidative activation of water molecule - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new catalyst precursor complex accelerating the progress of an oxidative dehydrogenation reaction of an organic substrate by the oxidative activation of water molecule. SOLUTION: The catalyst precursor complex for the dehydrogenation reaction from a carbon-hydrogen bond containing water as a ligand is expressed by general formula A (L1 is a tridentate ligand; R1 and R2 are each an alkyl, an aryl or an aralkyl or together form a (substituted)monocyclic or condensed ring group; M is a metal selected from the metals of the groups 6-9 of the periodic table; and Y<-> is an anion). The precursor complex forms a complex having a function of catalyzing the dehydrogenation from an organic compound by deprotonation and oxidation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to the above-mentioned general functions having a function of catalyzing a radical hydrogen atom abstraction reaction from a carbon-hydrogen bond of an organic compound by electrode oxidation or in combination with a mild oxidizing agent such as AgClO ^4. It is a technique relating to a catalyst precursor complex for a dehydrogenation reaction of an organic compound having a structure represented by the formula A and a complex represented by the general formula A.

[0002]

2. Description of the Related Art Conventionally, a technique for producing a hydrocarbon having a higher degree of unsaturation by dehydrogenating a hydrocarbon compound,
Also, a technique for producing aldehydes or ketones by oxidizing alcohols is known. The reaction is usually carried out using a deleterious metal oxide such as dichromic acid or permanganic acid as an oxidizing agent, or adding a catalyst to explosive peroxide. The reaction often suffered from toxicity and explosiveness of the oxidizing agent. Further, recent research on chemical reactions is to establish a technique for producing a target compound by an environmentally friendly method. And the environmentally friendly method is to finally establish a reaction system using a non-toxic catalyst using no solvent or a solvent mainly composed of water.

High valence transition metal-oxo complexes function as active species in biological and chemical oxidation of various organic substrates, and some ruthenium-oxo complexes have been reported as model compounds for in vivo enzymatic reactions. Has been done. Ruthenium-oxo complexes have been shown to form in the presence of molecular oxygen, peroxides such as hydrogen peroxide and ^t BuOOH, and oxygenating agents such as pyridine N oxide to hydroxylate and epoxidize hydrocarbons. Has been done. On the other hand, ruthenium
It is believed that -oxo complexes can also be formed by proton dissociation of ruthenium-aqua or hydroxo complexes. In this case, the oxidation reaction active species can be generated from the water molecule and the catalyst molecule by performing the chemical or electrochemical oxidation without using the above-mentioned oxygenating agent, and the reaction condition is mild in environment-friendly water. Allows oxidation reaction in (air, room temperature, potential near 0 V).
However, ruthenium-which is usually formed by such a method-
It is known that the oxo complex has a large basicity, and that the complexes are oxo-crosslinked to dimerize and further polymerize to lose the catalytic activity.

In such a situation, the present inventors [Ru (O
H₂) (3,5-^tBu₂Q) (terpy)]²⁺(3,
5-^tBu₂Q = 3,5-di (tert-butyl) -1,
2-benzoquinone, terpy = 2,2 ': 6', 2 "
-Terpyridine) is easily dimerized without dimerization.
It can dissociate the roton and form a ruthenium-oxo complex.
And revealed. Furthermore, at this time, from the oxo ligand
The intramolecular electron transfer to the quinone ligand causes the quinone ligand to
It is reduced to semiquinone and unpaired electrons are left on the oxo ligand.
It was proved to be induced. Furthermore, induced unpaired electrons
Complex having oxo ligand (oxyl radical ligand)
Ag which is a mild oxidizer⁺Caused by oxidation at
The complex makes the hydrogen atom radical from the C--H bond of the organic compound.
It has been shown that it has the ability to cut like a ru. Also, Ru
(OH) (3,6-^tBuQ) site (3,6-^tBuQ =
3,6- (tert-butyl) -1,2-benzoquino
Is btpyan (bis (2,2 ': 6', 2 "-
-Pyridyl) anthracene) ligands bridged by
Proton dissociation and oxidation from nuclear ruthenium-hydroxo complexes
The dinuclear ruthenium-oxo complex formed by
Excellent catalytic function for oxygen generation by child oxidation
I am reporting that. Dinuclear ruthenium-oxo complex?
The binuclear oxo complex derived from not only the oxidation of water,
Ag, a mild co-oxidant⁺In the presence of an aromatic hydride
Catalyzes the radical dehydrogenation of compounds to promote the degree of unsaturation.
Reported that corresponding aromatic compounds were obtained.
(Reference 1; Tohru Wada, Kiyoshi Tsuge and Koji Ta
naka, Chemistry Letters 2000, p910-911). The oxidative desorption
In the hydrogenation reaction, the water molecule coordinated on ruthenium is protonated.
It is progressing due to the double activation of dissociation and oxidation,
In the air, potential near 0V (Ag ⁺The reduction potential of is
Under moderate conditions, it is mildly + 0.4V vs SCE)
It should be noted that the condition is proceeding.

[0005]

An object of the present invention is to develop a catalyst having high activity and durability by advancing the method of the oxidative dehydrogenation reaction.

[0006]

In order to solve the above problems, the present inventors have proceeded with the development of a novel metal complex, developed the compound of the above general formula A, and carried out the oxidative dehydrogenation reaction of an organic compound. It was confirmed that the compound was useful as a catalyst precursor for the dehydrogenation reaction involved in, and succeeded in solving the above problems.
The first aspect of the present invention is a complex of a metal selected from the metals of Groups 6 to 9 of the periodic table containing the dithiolene represented by the general formula A as a ligand. Preferably, in the compound represented by the general formula A, M is selected from Ru, Cr or Co, and R ₁ and R ₂ are saturated or unsaturated cyclic substituents formed by bonding of both. A complex of the above metal having the structure of the general formula B, more preferably a tridentate ligand having a 2,2 ′: 6 ′, 2 ″ -terpyridine derivative,
Alternatively, it is a complex of each metal, which is a 1,4,7-triazacyclononane derivative.

The second aspect of the present invention is to produce a metal complex having the function of catalyzing a radical hydrogen atom abstraction reaction from a carbon-hydrogen bond of an organic compound by receiving proton dissociation and oxidative activation. Is a catalyst precursor complex for an organic compound dehydrogenation reaction containing water as a ligand. Preferably, in the compound represented by the general formula A, M is selected from Ru, Cr or Co, and R ₁ and R ₂ are saturated or unsaturated cyclic substituents formed by bonding of both. A catalyst precursor complex for a dehydrogenation reaction of the organic compound, which is characterized by a structure represented by the general formula B, and more preferably a tridentate ligand having 2,2 ′: 6 ′,
A catalyst precursor complex for a dehydrogenation reaction of each of the above organic compounds, which is a 2 ″ -terpyridine derivative or a 1,4,7-triazacyclononane derivative.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail. A. The metal complex containing the dithiolene ligand of the present invention is
Although the compound represented by the general formula A is preferred,
L1 is 2,2 ': 6', 2 "-terpyridine, M
Is Ru^IIAnd R₁And R₂Is an alkyl group, phenyl
Group or both bound to 3,4-tert-butyl group
Ring, 3-methylbenzene ring, or halogen
A compound forming a substituted benzene ring may be mentioned.
More preferably, [Ru (trpy) (pdt) (O
H²)] (CF³SO³)², [Ru (trpy) (tb
t) (OH²)] (CF³SO³)², [Ru (trpy)
(C⁶H⁸S ²) (OH²)] (CF³SO³)², (Abbreviation;
trpy = 2,2 ′: 6,2 ″ -terpyridine, pd
t = 1,2-diphenyldithiolene, tbt = 4-methyl
Ru-1,2-dibenzoquinone, C⁶H⁸S²= Cyclohex
Syl-1,2-ditin) can be mentioned.

B. The complex compound and the oxidizing agent AgClO ⁴
A reaction cycle for the oxidative dehydrogenation of a hydrocarbon compound to produce the corresponding more highly unsaturated hydrocarbon using the base ^t BuOK is shown in FIG. In the reaction, a hydroxo complex and an oxo complex are formed by proton dissociation from water molecules coordinated on M (ruthenium). At this time, intramolecular electron transfer occurs from the oxo ligand with increased electron density to the dithiolene ligand, and as a result, the dithiolene ligand becomes a dithiolene anion radical ligand and the oxo ligand becomes an oxyl radical coordination. Converted to child. Changes in these metal complexes were confirmed by absorption spectrum and cyclic voltammetry. Changes in absorption spectra of the ruthenium-oxo-dithiolene complex and the ruthenium-oxyl radical-dithiolene complex are shown in FIG. 2, and cyclic voltammetry is shown in FIG. In the reaction, the dithiolene anion radical ligand of the ruthenium-oxo complex is the oxidizing agent Ag ⁺
The ruthenium-oxyl radical-dithiolene complex formed by being oxidized by becomes a catalytically active species and proceeds by radically abstracting a hydrogen atom from the organic compound. That is, the reaction is characterized in that it proceeds using the redox reaction of the dithiolene ligand as a driving force.

C. For use in combination with oxidative dehydrogenation reaction
As the oxidant that can be used, AgClO ^Four, (NH^Four) Ce
(IV) (NO³)⁶And so on. Also,
To proceed the dehydrogenation reaction, use a base to adjust the pH to 9 or more.
It should be above,^tBuOK and NaOH are preferred
Can be mentioned as.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples. Example 1 [Ru (trpy) (pdt) (OH ² )] (CF ³ SO
³ ) Synthesis of ² . [Ru (dmso) (pdt) (trpy)] (Reference 2: Hideki Sugimoto, Kiyoshi Tsuge and Koji Tanak
a, JCS Dalton Trans., 2001, p 57 63) 50m
g was suspended in 10 mL of methanol, and HCF ₃ SO ₃ 14
Add μL and stir for 4 hours. Unnecessary substances are filtered, the filtrate is concentrated under reduced pressure, and THF is added to obtain 52 mg in yield. NMR (ppm): 9.02 (2H, d), 8.76 (3H, m), 8.21 (2H, t), 7.
78 (2H, d), 7.58 (1H, t), 7.2-7.55 (11H, m). ESI-MS: 29
7.5 ([M] ²⁺ ).

Example 2 [Ru (trpy) (tdt) (OH ² )] (CF ³ SO
³ ) Synthesis of ² . [Ru (dmso) (tdt) (trpy)] (Reference 2: Hideki Sugimoto, Kiyoshi Tsuge and Koji Tanaka,
JCS Dalton Trans., 2001, p 57 63) 57 mg
Is suspended in 10 mL of methanol, and HCF ₃ SO ₃ 100 is added.
Add μL and stir for 4 hours. Unnecessary substances are filtered, the filtrate is concentrated under reduced pressure, and then dried in vacuum to obtain 15 mg in yield. NMR (ppm): 9.08 (3H, t), 8.83 (2H, d), 8.73 (2H,
d), 8.56 (1H, t), 8.08 (4H, dt), 7.72 (2H, d), 7.
33 (1H, t), 6.83 (2H, m), 2.39, 2.35 (3H, s). ESI
-MS; 253 ([M] ²⁺ ).

Example 3 [Ru (trpy) (C ⁶ H ⁸ S ² ) (OH ² )] (CF ³
Synthesis of SO ³ ) ² . 4,5-Cyclohexano-1,3-dithiol-2-one (Reference 3: A
jit K. Bhattacharya and Alfred G. Hortmann, J. Org.
Chem., 39, p95-97, 1974) 83 mg was added to 150 mL of methanol, and CsOH (162 mg) was added to the solution.
Was added. Stir for 10 minutes, then add [Ru (dmso) Cl ₂
(Trpy)] 200 mg was added and the mixture was heated under reflux for 4 hours.
After allowing to cool, it was filtered and dried. Obtained in a yield of 210 mg. 83 mg of the obtained compound was dissolved in 10 mL of methanol,
35 mL of HCF ₃ SO _{3 was} added dropwise and stirred for 4 hours. Unwanted substances were filtered and then concentrated under reduced pressure to dryness. Obtained in a yield of 28 mg. NMR (ppm): 9.05 (2H, d), 8.78 (3H, t), 8.25 (2
H, t), 7.50 (4H, q), 3.62 (4H, m), 3.32 (4H, m). ESI-MS; 628 ({M-H ₂ O + CF ₃ S
O ₃ } ⁺ ).

Example 4 A method for synthesizing an aldehyde by benzyl alcohol oxidative dehydrogenation using the compound synthesized in Example 1 as a catalyst will be described. [Ru (trpy) (pdt) (OH ² )] (CF ³ SO
³ ) ² (4.1 mg, 4.8 μmol, 1.0 mol% with respect to the used benzyl alcohol) in an acetone / water mixed solution (5/95, 1.0 ml) was added with benzyl alcohol (25 μL,
0.24 mmol), Ce (NH ₄ ) ₂ (NO ₃ ) ₆ (27
4 mg, 0.50 mmol) in this order, and stirred at room temperature in the air for 1 hour. Acetone was removed from the reaction solution under reduced pressure and then extracted with ether. Benzaldehyde yield 2
Produce at 8%. 28 catalyst turnovers.

Example 5 Using the compound synthesized in Example 1 as a catalyst, 9,10-
A method for synthesizing anthracene by an oxidative dehydrogenation reaction of dihydroanthracene will be described. [Ru (trpy) (pdt) (OH ² )] (CF ³ SO
³ ) ² (5.0 mg, 6.0 μmol) in acetone solution (0.5 mL) with 9,10-dihydroanthracene (0.54 mg, 3.0 μmol) and AgCF ₃ SO _3.
3 (1.54 mg, 6.0 μmol) is added. To this solution is added ^t BuOK (0.67 mg, 6.0 mmol). The reaction was completed almost instantly and yielded anthracene in a yield of 40
Generate in%.

[0016]

As described above, by using the dithiolene complex of the present invention, oxidative activation of water molecules is carried out under relatively mild conditions without using an oxygenating agent such as peroxide, The excellent effect that the oxidative dehydrogenation reaction of an organic substrate can be advanced in a solvent system mainly composed of environment-friendly water is brought about.

[Brief description of drawings]

FIG. 1 shows a catalytic cycle of a dehydrogenation reaction of an organic compound using the metal complex of the present invention as a catalyst precursor.

FIG. 2 Absorption spectra of aqua-dithiolene complex of metal complex of the present invention and oxo-dithiolene anion radical complex

FIG. 3 shows the cyclic voltammetry measurement values of the metal complex of the present invention, aqua-dithiolene complex (a) and oxo-dithiolene anion radical complex (b).

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideki Sugimoto             2-438 Higashi Ueno Shibamachi, Sakai City, Osaka Prefecture Osaka City             Tate University Public Building 12 F term (reference) 4G069 AA06 BA27A BA27B BC58A                       BC67A BC70A BC70B BE21A                       BE21B BE33A BE34A BE34B                       BE36A BE36B CB07 CB72                 4H006 AA01 AB40 TC10                 4H050 AA01 AA03 AB40 WB14 WB15

Claims (6)

[Claims] 1. A general formula A having a function of catalyzing a radical hydrogen atom abstraction reaction from a carbon-hydrogen bond of an organic compound by undergoing proton dissociation and oxidative activation.
A catalyst precursor complex for a dehydrogenation reaction of an organic compound containing water as a ligand represented by: [Chemical 1] However, in the general formula A, L1 is a tridentate ligand, R ₁ and R ₂ are an alkyl group, an aryl group, or a monocyclic or condensed ring which may have a substituent formed by bonding of both. Is. M is a metal selected from metals of Groups 6 to 9 of the periodic table. Y ^- is an anion. 2. In the compound represented by the general formula A, M is selected from Ru, Cr or Co, and R ₁ and R ₂ are saturated or unsaturated cyclic substituents formed by the bonding of both. The catalyst precursor complex for the dehydrogenation reaction of an organic compound according to claim 1, which has a structure represented by the general formula B, wherein: [Chemical 2] (However, M is selected from Ru, Cr or Co, and L
1, Y ⁻ are the same as in the general formula A. R ₃ , R ₄ , R ₅ and R ₆ are independently selected from alkyl groups, halogens and aryl groups. Dotted lines show the case with and without binding. ) 3. The tridentate ligand is a 2,2 ′: 6 ′, 2 ″ -terpyridine derivative or a 1,4,7-triazacyclononane derivative, as claimed in claim 1 or 2.
A catalyst precursor complex for the dehydrogenation reaction of the organic compound described in 1. 4. A complex of a metal selected from the metals of groups 6 to 9 of the periodic table containing the dithiolene represented by the general formula A as a ligand. 5. In the compound represented by the general formula A, M is selected from Ru, Cr or Co, and R ₁ and R ₂ are saturated or unsaturated cyclic substituents formed by the bonding of both. The metal complex according to claim 4, which is a compound having a structure represented by the general formula B. 6. The tridentate ligand is a 2,2 ′: 6 ′, 2 ″ -terpyridine derivative or a 1,4,7-triazacyclononane derivative, as claimed in claim 4 or 5.
Complexes of the described metals.