JP2004345964A - Trivalent ruthenium ammine complex compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new ruthenium-containing complex catalyst for electrochemical oxidation reaction. <P>SOLUTION: This new compound is expressed by formula: [Ru<SP>III</SP>(NH<SB>3</SB>)(3,5-<SP>t</SP>BuSQ)(trpy)]<SP>2+</SP>A<SP>2-</SP>(trpy: terpyridine A: anion SQ: semiquinonate radical anion) and catalyzes oxidation of an alcohol, especially 2-propanol, under an alkaline condition and an electrochemical condition. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a complex compound of the above formula 1 containing a novel Ru which catalyzes a reaction of oxidizing an alcohol such as methanol under a basic electrochemical composition.
[0002]
[Prior art]
BACKGROUND ART Complex catalysts having oxidation-reduction ability have been studied with the aim of constructing a fuel cell that uses alcohols as fuel and takes out electric power by electrochemical oxidation at the cathode of the fuel. Under such circumstances, an o-quinone-containing Ru quinone aqua complex having terpy (2,2 ′: 6,2 ″ -terpyridine) as a ligand has been synthesized, and the redox behavior accompanying proton dissociation has been studied. However, from the technical point of view of the construction of the fuel cell system, it is at the stage of the synthesis of the oxidation catalyst complex and the study of its characteristics. However, it has been clarified that the complex catalysts studied in the development stage function as oxidation catalysts in various reaction systems.
[0003]
[Patent Document 1]
JP-A-2000-48848 (published on Feb. 18, 2000), Claims, Table 1
[0004]
In the above-mentioned research, Patent Literature 1 discloses that an o-quinone-containing Ru quinone aqua complex having terpy (2,2 ′: 6 ′, 2 ″ -terpyridine) as a ligand is used as a redox species to form a hydrogen ion An electromotive force system is constructed from an electrode cell I whose oxidation-reduction potential fluctuates depending on the concentration and an electrode cell II containing a reducing species, and a conversion system using the hydrogen ion concentration fluctuation as electric energy has been proposed. Has not been completed.
[0005]
[Problems to be solved by the invention]
An object of the present invention is to provide a novel Ru-containing complex compound which is highly usable in a redox system during the development. In order to solve the above problem, [Ru ^III (OH ₂ ) (3,5- ^t BuSQ) (trpy),] ²⁺ (ClO ₄ ) ₂ to [Ru ^III (NH ₃ ) (3,5- ^t BuSQ) (Trpy),] ²⁺ (ClO ₄ ) ₂ was synthesized, and its redox properties under basic electrochemical composition were examined, and found to be effective as a catalyst in the oxidation reaction of alcohols, particularly 2-propanol. The above problem was solved.
[0006]
[Means for Solving the Problems]
The present invention is a novel compound which catalyzes the oxidation of alcohol in the _{^{[Ru III (NH 3) (3,5-}} t BuSQ) (trpy), ] Electrochemical conditions in alkaline conditions is ²⁺ A ^-2 . Preferably, the novel compound catalyzes the oxidation of the alcohol, wherein the alcohol is 2-propanol.
[0007]
[Embodiment of the present invention]
The present invention will be described in more detail.
A. The features of the present invention will be described with reference to FIG. 1 which describes the concept of the mechanism of 2-propanol oxidation using the novel compound as an oxidation catalyst.
[Ru ^III (NH ₃ ) (3,5- ^t BuSQ) (terpy),] ²⁺ dissociates proton H ⁺ from ammine ligand NH ₃ by a base. Was increased electron density and by proton dissociation _(NH 2) ^- electron transfer occurs from the ligands to the central metal ruthenium (III), ruthenium to one-electron reduction ruthenium _{(II), (NH 2)} - coordination The electron is one-electron oxidized and converted to an amino radical ligand, NH ₂ , which induces an unpaired electron on N. That is, reactive species ruthenium divalent amino radical complex _{^{[Ru II (NH 2) (3,5-}} t BuSQ) (terpy), ] is converted into ^+. The reactive species undergoes a radical hydrogen abstraction reaction from 2-propanol to regenerate the ruthenium trivalent ammine complex. The generated organic radicals dissociate protons under basic conditions and undergo electrode oxidation to produce acetone.
[0008]
This reaction was confirmed by the following spectroscopic and electrochemical methods.
A. Spectroscopic considerations by UV-visible near-infrared absorption spectrum.
In a dichloromethane solution, [Ru ^III (NH ₃ ) (3,5- ^t BuSQ) (terpy),] ²⁺ exhibits a 615 nm (ε 13000 Mcm ⁻¹ ) absorption characteristic of a ruthenium trivalent-semiquinone complex. addition of 1.0 equivalents of base ^t BuOK methanol solution for absorption of 615nm disappears, a new absorption of 854nm was observed. This change is reversibly reversed by the addition of the acid. This absorption at 854 nm is characteristic of a ruthenium divalent-semiquinone complex. That is, it was proved that [Ru ^III (NH ₃ ) (3,5- ^t BuSQ) (terpy),] ²⁺ was reduced from ruthenium trivalent to ruthenium divalent by adding a base.
FIG. 2 shows an ultraviolet-visible-near-infrared absorption spectrum in each state.
[0009]
B. Electrochemical considerations.
Here, by measuring cyclic voltammetry in a dichloromethane solution, [Ru ^III (NH ₃ ) (3,5- ^t BuSQ) (terpy),] ²⁺ is +0.00 V (vs Ag / Ag ⁺ ) and ruthenium. It was found that the trivalent was reversibly reduced to ruthenium divalent. In addition, the natural electrode potential of [Ru ^III (NH ₃ ) (3,5- ^t BuSQ) (terpy),] ²⁺ was observed at +0.15 V on the positive side of +0.00 V. When 1.0 equivalent of ^t BuOK methanol solution is added to the complex as a base, the natural electrode potential shifts to −0.48 V on the negative side of the redox potential of Ru (II) / Ru (III). did. This result indicates that [Ru ^III (NH ₃ ) (3,5- ^t BuSQ) (terpy)] ²⁺ was reduced from ruthenium trivalent to ruthenium divalent by addition of a base.
FIG. 3 shows the measurement results of cyclic voltammetry.
[0010]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples.
Measuring equipment used;
UV-visible near-infrared absorption spectrum; UV-3100PC (Shimadzu Corporation) cyclic voltammetry; Electrochemical Analyzer Model 650 (manufactured by ALS)
[0011]
Example 1
A, Synthesis of [Ru ^III (NH ₃ ) (3,5- ^t BuSQ) (terpy),] ²⁺ (ClO ₄ ) ₂ ;
Reference [Bull. Chem. Soc. Jpn. , 73 607-614 (2000) was synthesized by the method described in] _{^{[Ru III (OH 2) (3,5-}} t BuSQ) (terpy), ] ²⁺ was dissolved _{(ClO 4) 2} in methylene chloride, the Excess NH ₃ aqueous solution dissolved in tetrahydrofuran was added to the solution, and the mixture was stirred at room temperature for 24 hours. After the solvent removed under reduced pressure, the resulting _{^{[Ru III (NH 3) (3,5-}} t BuSQ) (terpy) ] ²⁺ _{(ClO 4) 2} was purified using basic alumina column.
[0012]
B, Oxidation reaction of an electrochemical catalyst of alcohols (1), oxidation reaction in 2-propanol solution;
[Ru ^III (NH ₃ ) (3,5- ^t BuSQ) (trpy),] ²⁺ (ClO ₄ ) ₂ is dissolved in a 2-propanol solution of the electrolyte ⁿ Bu ₄ NBF ₄ and the base ^t BuOK. Cyclic voltammetry was measured using a glassy carbon electrode as a working electrode, a platinum wire as a counter electrode, and Ag / Ag ⁺ as a reference electrode (FIG. 4).
At +0.2 V or more, a large oxidation current was observed. From this, it was found that the catalytic oxidation reaction of the complex of 2-propanol was in progress.
[0013]
(2) an oxidation reaction in a methanol solution;
Cyclic voltammetry was measured using methanol instead of 2-propanol in (1) (FIG. 5). An oxidation current resulting from the catalytic oxidation of methanol was observed. However, the amount of current was smaller than in the case of 2-propanol. Incidentally, when an oxo radical complex formed by using [Ru ^III (OH ₂ ) (3,5- ^t BuSQ) (terpy)] ²⁺ instead of the amino radical complex, the catalytic activity was low.
[0014]
【The invention's effect】
As described above, the ruthenium trivalent ammine complex provided by the present invention is a more effective oxidation catalyst for alcohols than the conventional ruthenium-containing complex, and is used for constructing the fuel cell system of the final object. It contributes to the industry in providing reference information.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a cycle in the catalytic oxidation reaction of alcohols of a ruthenium trivalent ammine complex of the present invention. FIG. 2 is a diagram showing the conversion of a ruthenium (III) ammine complex to a ruthenium divalent amino radical complex in a cycle. Verification by UV-Vis near-infrared absorption spectrum [Fig. 3] Cyclic voltammetry for verification of reversible reaction between ruthenium trivalent ammine complex and ruthenium divalent amino radical complex [Fig. 4] [Ru ^III (NH ₃ ) (3 5- ^t BuSQ) (trpy),] ²⁺ _{(ClO 4)} cyclic voltammetry [5] of ₂ to electrochemical oxidation catalyst 2-propanol oxidation reaction ^[Ru III _(NH 3) _(3,5- ^t BuSQ) (trpy),] ²⁺ (ClO ₄ ) ₂ as an electrochemical oxidation catalyst Cyclic voltammetry of oxidation reaction

Claims (2)

Represented by the following formula 1 _{^{[Ru III (NH 3) (3,5-}} t BuSQ) (trpy), ] ²⁺ A novel that catalyzes the oxidation of alcohol in the electrochemical conditions at alkaline conditions is ^2- Compound

A is an anion atom or an atomic group. The novel compound catalyzing the oxidation of an alcohol according to claim 1, wherein the alcohol is 2-propanol.

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