JP5801662B2 - Substrate oxidation method - Google Patents

Description

  The present invention relates to a substrate oxidation method, a rhodium terpyridine aqua complex used in the oxidation method, a rhodium terpyridine low valence complex used in the oxidation method, a rhodium terpyridine hydride complex used in the oxidation method, and a rhodium used in the oxidation method. Terpyridine dinuclear complex, rhodium terpyridine peroxo complex used in the oxidation method, method for producing rhodium terpyridine low valence complex, method for producing rhodium terpyridine hydride complex, method for producing rhodium terpyridine dinuclear complex and rhodium terpyridine The present invention relates to a method for producing a peroxo complex.

  The oxidation reaction using oxygen molecules as an oxidizing agent is an important issue in terms of cost or safety because it exhibits a wide range of reactivity and abundant oxygen molecules exist in the environment. However, oxygen molecules are very poor as they are, and an oxidation reaction using oxygen molecules tends to cause undesirable side reactions. Furthermore, it is often necessary to heat at a high temperature to accelerate the reaction rate.

  In order to avoid such problems, a more active peroxide or oxygen anion is usually used. However, these peroxides or oxygen anions are expensive and are dangerous to handle.

Design of an appropriate catalyst is important for oxidation using oxygen molecules, and molecular design such as controlling the approach of a substrate while activating oxygen molecules is necessary. As a catalyst used for the oxidation of oxygen molecules, for example, cytochrome P450, which is a biological enzyme, is reductively activated by giving two electrons to oxygen molecules to produce highly reactive peroxo (O ₂ ²⁻ ). (Non-Patent Document 1). Cytochrome P450 can be activated by two-electron reduction of oxygen molecules at the metal ion (Fe) center (hereinafter also referred to as reductive activation), and can perform a controlled oxidation reaction.

  As reductive activation of oxygen molecules, examples have been reported in which oxygen molecules are activated by various reducing agents such as ascorbic acid, and the oxygen molecules are used as an oxidizing agent for substrate oxidation reactions (Non-patent Documents). 2).

  Non-Patent Document 3 discloses an oxidation reaction (epoxidation) using hydrogen as a reducing agent and a manganese complex. However, in the oxidation reaction described in Non-Patent Document 2, colloidal Pt is added and it is not a homogeneous or single catalyst.

Non-Patent Document 4 discloses a reaction in which oxygen is activated through a hydride intermediate using hydrogen as a reducing agent. However, in the reaction disclosed in Non-Patent Document 4, the activated oxygen is water according to the following reaction formula.
H ₂ + 1 / 2O ₂ → H ₂ O

  Further, Patent Documents 1 and 2 disclose a substrate oxidation reaction using hydrogen and oxygen in a heterogeneous system.

On the other hand, a homogeneous complex catalyst (NiRu complex) that extracts electrons from hydrogen by the following reaction formula by pH control at room temperature and normal pressure in water has been reported (Patent Document 3 and Non-Patent Document 5). The electrons extracted by the complex are used for Cu ²⁺ reduction, but are not used for other reactions.
H ₂ → 2H ⁺ + 2e ⁻

JP-A-8-269029 JP 2010-64972 A JP 2009-235044

J. et al. Am. Chem. Soc. 1979, 101, p. 1032-1033 J. et al. Biol. Chem., 1954, 208, p. 731-739. J. et al. Am. Chem. Soc. 1981, 103, p. 7371-7373. J. et al. Am. Chem. Soc. 2009, 131, p. 5001-5009. Science, 2007, 316, p. 585-587.

  However, the reaction of reductively activating oxygen molecules in a heterogeneous system and oxidizing the substrate with the oxygen molecules has a problem that the substrate conversion rate and the product selectivity are low. Further, in this reaction, since an oxidizing agent and a reducing agent coexist in the system, it is necessary to devise such that the oxidizing of the reducing agent proceeds independently of the oxidation of the substrate and the oxidation of the substrate proceeds selectively.

  Accordingly, the present invention provides a method for oxidizing a substrate in which an oxidizing agent and a reducing agent are separately introduced into the system, and the reductive activation of oxygen molecules and the oxidation of the substrate are performed on a homogeneous system and a single complex. This is the issue.

  As a result of examining the above problems, the present inventors use a rhodium terpyridine aqua complex and use hydrogen as a reducing agent to reductively activate oxygen molecules in a homogeneous system and oxidize the substrate by the oxygen molecules. The present invention has been completed by finding out what can be done.

That is, the present invention is as follows.
1. A method for oxidizing a substrate comprising the following steps A, B, D, E or the following steps A, C, D, E.
(Step A) The rhodium terpyridine aqua complex (M) represented by the following formula (1) is allowed to act on the hydrogen molecule (H ₂ ) to extract electrons from the hydrogen molecule, and represented by the following reaction formula: And a step of holding electrons in the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2):
2H ₂ + 2M → 4H ⁺ +2 [M + 2e ⁻ ]
(Step B) As represented by the following reaction formula, the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2) is reacted with a proton, and represented by the following formula (3). The following formula (4) is obtained by reductive elimination of hydrogen via a rhodium terpyridine hydride complex (MH).
Rhodium terpyridine binuclear complex _(M 2 + 2e represented by) ^-) step to produce a ^{2 [M + 2e -] +} 2H + → 2 [MH] → H 2 + [M 2 + 2e -]
(Step C) As represented by the following reaction formula, rhodium terpyridine represented by the following formula (4) is obtained by oxidation of the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2). Step of generating a binuclear complex (M ₂ + 2e ⁻ ) 2 [M + 2e ⁻ ] → 2e ⁻ + [M ₂ + 2e ⁻ ]
(Step D) As represented by the following reaction formula, the rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) is reacted with oxygen (O ₂ ), and the following formula ( 5) Step of producing a rhodium terpyridine peroxo complex represented by [M ₂ + 2e ⁻ ] + O ₂ → [M ₂ O ₂ + 2e ⁻ ]
(Step E) As represented by the following reaction formula, the rhodium terpyridine peroxo complex (M ₂ O ₂ + 2e ⁻ ) represented by the following formula (5) is reacted with the substrate (Q) to oxidize the substrate. Process [M ₂ O ₂ + 2e ⁻ ] + Q + 2H ⁺ + H ₂ O → 2M + QO
[In the above reaction formula, Q is triphenylphosphine. ]

[In the formula (1), X and Y are each H ₂ O or OH ⁻ (except that both X and Y are OH ⁻ ) . ]

[In the formula (2), X is _{H 2} O. ]

[In the formula (3), X is _{H 2} O. ]

[In the formula (4), X is _{H 2} O. ]

[In formula (5), X is _{H 2} O. ]
2. A rhodium terpyridine aqua complex (M) represented by the following formula (1) used in the oxidation method according to item 1.

[In the formula (1), X and Y are each H ₂ O or OH ⁻ (except that both X and Y are OH ⁻ ) . ]
3. A rhodium terpyridine low-valence complex (M ₂ + 2e ⁻ ) represented by the following formula (2) used in the oxidation method according to item 1.

[In the formula (2), X is _{H 2} O. ]
4). A rhodium terpyridine hydride complex (MH) represented by the following formula (3) used in the oxidation method according to item 1.

[In the formula (3), X is _{H 2} O. ]
5. The rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) used in the oxidation reaction described in item 1 above.

[In the formula (4), X is _{H 2} O. ]
6). A rhodium terpyridine peroxo complex (M ₂ O ₂ + 2e ⁻ ) represented by the following formula (5) used in the oxidation method according to item 1.

[In formula (5), X is _{H 2} O. ]
7). The rhodium terpyridine aqua complex (M) represented by the following formula (1) is allowed to act on the hydrogen molecule (H ₂ ), and electrons are extracted from the hydrogen molecule. A method of holding electrons in the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by (2).
2H ₂ + 2M → 4H ⁺ +2 [M + 2e ⁻ ]

[In the formula (1), X and Y are each H ₂ O or OH ⁻ (except that both X and Y are OH ⁻ ) . ]

[In the formula (2), X is _{H 2} O. ]
8). As represented by the following reaction formula, a rhodium terpyridine represented by the following formula (3) is obtained by reacting a proton with the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2). A method for producing a rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) by reductive elimination of hydrogen via a hydride complex (MH).
2 [M + 2e ⁻ ] + 2H ⁺ → 2 [MH] → H ₂ + [M ₂ + 2e ⁻ ]

[In the formula (2), X is _{H 2} O. ]

[In the formula (3), X is _{H 2} O. ]

[In the formula (4), X is _{H 2} O. ]
9. As represented by the following reaction formula, the rhodium terpyridine binuclear complex represented by the following formula (4) is obtained by the oxidation action of the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2). A method of generating (M ₂ + 2e ⁻ ).
2 [M + 2e ⁻ ] → 2e ⁻ + [M ₂ + 2e ⁻ ]

[In the formula (2), X is _{H 2} O. ]

[In the formula (4), X is _{H 2} O. ]
10. As represented by the following reaction formula, the rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) is reacted with oxygen (O ₂ ), and is represented by the following formula (5). To produce a rhodium terpyridine peroxo complex.
[M ₂ + 2e ⁻ ] + O ₂ → [M ₂ O ₂ + 2e ⁻ ]

[In the formula (4), X is _{H 2} O. ]

[In formula (5), X is _{H 2} O. ]
11. A method of oxidizing a substrate by reacting a rhodium terpyridine peroxo complex (M ₂ O ₂ + 2e ⁻ ) represented by the following formula (5) with a substrate (Q) as represented by the following reaction formula.
[M ₂ O ₂ + 2e ⁻ ] + Q + 2H ⁺ + H ₂ O → 2M + QO
[In the above reaction formula, Q is triphenylphosphine. ]

[In formula (5), X is _{H 2} O. ]

  According to the substrate oxidation method of the present invention, since it is a reaction system in which hydrogen and oxygen which are reducing agents are separately introduced into the system, simple oxidation of the reducing agent (hydrogen), which has been a problem, is prevented and explosion occurs. The danger of can be avoided.

FIG. 1 shows an ORTEP diagram of rhodium terpyridine aqua complex [1a] (NO ₃ ) ₃ obtained by X-ray analysis. FIG. 2 shows an ORTEP diagram of rhodium terpyridine aqua complex [1b] (NO ₃ ) ₂ obtained by X-ray analysis. FIG. 3 shows the results of pH titration of rhodium terpyridine aqua complex [1a] (NO ₃ ) ₃ . FIG. 4 shows an ORTEP diagram of a rhodium terpyridine low valence complex [2b] (CF ₃ SO ₃ ) obtained by X-ray analysis. FIG. 5 shows the results of analysis of rhodium terpyridine hydride complex [3b] (CF ₃ SO ₃ ) ₂ by ¹ H NMR spectroscopy. FIG. 6 shows an ORTEP diagram of rhodium terpyridine binuclear complex [4b] (CF ₃ SO ₃ ) ₄ obtained by X-ray analysis. FIG. 7 shows an ORTEP diagram of rhodium terpyridine peroxo complex [5b] (CF ₃ SO ₃ ) ₄ obtained by X-ray analysis. 8 (a) is rhodium terpyridine peroxo complex _{[5b] (CF 3 SO 3} ) 4 Raman spectrum, FIG. 8 (b) ^[5b which is labeled with ¹⁸ O] rhodium terpyridine peroxo complex _(CF 3 SO ₃ ) The Raman spectrum of ₄ is shown. FIGS. 8 (a) and 8 (b) show Raman spectra of rhodium terpyridine peroxo complex [5b] excited with 532 nm laser and produced with ¹⁶ O ₂ and ¹⁸ O ₂ respectively. FIG. 8 (c) is a difference spectrum between FIG. 8 (a) and FIG. 8 (b). FIG. 9 shows the change over time according to the UV-vis spectrum during the reaction of the rhodium terpyridine low valence complex [2b] with oxygen. FIG. 10 shows a reaction scheme in the oxidation reaction of triphenylphosphine using a hydrogen / oxygen mixed gas. (Comparative Example 1) FIG. 11 shows a reaction scheme in a continuous oxidation reaction of triphenylphosphine. (Example 7) FIG. 12 shows the yield in the oxidation reaction of triphenylphosphine.

<Rhodium terpyridine aqua complex>
In the substrate oxidation method of the present invention, a rhodium terpyridine aqua complex (M) represented by the following formula (1) is used as a starting material.

In the formula (1), X and Y each is _{H 2} O or OH ^- is. Hereinafter, the case where X and Y are H ₂ O is referred to as [1a], and the case where X is OH and Y is H ₂ O is referred to as [1b]. The case where X and Y are OH is [1c], and the case where the H ₂ O ligand of [1c] is replaced by OH is [1d].

The rhodium terpyridine aqua complex [1a] represented by the formula (1) can be prepared by the following method. Rh ^III (terpyl) Cl ₃ is prepared by the method described in the literature (Inorg. Chem., 1998, 37, 5733-5742). The rhodium terpyridine aqua complex [1a] is obtained by stirring the Rh ^III (terpy) Cl ₃ solution under N ₂ , preferably for 6-12 hours under nitrogen atmosphere at room temperature, and removing the precipitated AgCl by filtration. .

When analyzing the structure of the rhodium terpyridine aqua complex [1b], a solution of Rh ^III (terpy) Cl ₃ and AgNO ₃ in H ₂ O (pH 7) is preferably 6 under N ₂ as described later in the Examples. [1b] (NO ₃ ) ₂ can be obtained by stirring for -12 hours under a nitrogen atmosphere at room temperature and removing the precipitated AgCl by filtration to analyze the structure.

In addition, when the rhodium terpyridine aqua complex [1a] is structurally analyzed, as described later in Examples, a solution of [1 a ] (NO ₃ ) ₃ in MeOH to which 0.1% by mass of nitric acid has been added, By slowly adding ether, [1a] (NO ₃ ) ₃ can be obtained for structural analysis.

As shown in FIG. 1, the rhodium terpyridine aqua complex [1a] represented by the formula (1) is based on an Rh ^III core fixed to a terpyridine ligand, and includes three aqua ligands (or Depending on pH, as shown in FIG. 2, it has two aqua ligands and one hydroxo ligand.

  As shown in FIG. 3, rhodium terpyridine aqua complex [1a] has three inflection points in pH titration, and each pKa is

It is.

<Rhodium terpyridine low valence complex>
By allowing a hydrogen molecule (H ₂ ) to act on the rhodium terpyridine aqua complex, electrons are extracted from the hydrogen molecule, and the rhodium terpyridine represented by the following formula (2) is represented by the following reaction formula: A low valence complex (M + 2e ⁻ ) (hereinafter also referred to as rhodium terpyridine low valence complex [2a]) is formed.
2H ₂ + 2M → 4H ⁺ +2 [M + 2e ⁻ ]

In the formula (2), X is H ₂ O.

The rhodium terpyridine low valence complex is formed by the following method. The rhodium terpyridine aqua complex activates hydrogen molecules (H ₂ ) in a heterolytic manner, and the rhodium terpyridine hydride complex (MH) described later is formed. It is considered that a rhodium terpyridine low valence complex is formed by the action of the terpyridine hydride complex.

Rhodium terpyridine low valent complex, as described below in the Examples, the pH of the solution (3 ml) of the rhodium terpyridine aqua complex in _{H 2} O, preferably 0.01~1.0M NaOH _{/ H} 2 O It is preferably obtained by reacting the obtained solution with hydrogen preferably at 15 to 35 ° C., preferably 0.1 to 0.8 MPa, after adjusting to 2.0 to 13.0 by addition of.

When analyzing the structure of a rhodium terpyridine low valence complex, as will be described later in the Examples, [2a] (NO ₃ ) added with NO ₃ to the rhodium terpyridine low valence complex [2a] represented by the formula (3) ₃ ) Dissolve the solid sample in NaOTf in CH ₃ CN and add diethyl ether to the resulting purple solution.

As a result, the resulting solution was allowed to stand for several days, and a purple crystal {[2b] (CF) of rhodium terpyridine low valence complex (hereinafter also referred to as [2b]) in which X is CH ₃ CN in the formula (2). ₃ SO ₃ )}, and the structure of the crystal can be analyzed.

The rhodium terpyridine low-valence complex [2b] (CF ₃ SO ₃ ) is obtained by substituting the counter anion of NO ₃ ^— with CF ₃ SO ₃ ^— in acetonitrile. FIG. 4 shows the structure of a rhodium terpyridine low-valence complex [2b] (CF ₃ SO ₃ ) obtained by X-ray analysis. As shown in FIG. 4, the rhodium ion in the rhodium terpyridine low-valence complex is located at the center of a planar square structure composed of one terpyridine and one CH ₃ CN ligand.

<Rhodium terpyridine hydride complex>
As shown in the following reaction formula, rhodium terpyridine hydride complex [3b] (CF ₃ SO ₃ ) ₂ is added to a trifluoride as a proton source in an acetonitrile solution of rhodium terpyridine low valence complex [2b] (CF ₃ SO ₃ ). It can be obtained by adding romethanesulfonic acid (CF ₃ SO ₃ H).

In the formula (3), X is CH ₃ CN. Hereinafter, the rhodium terpyridine hydride complex in which X is CH ₃ CN in the formula (3) is also referred to as a rhodium terpyridine hydride complex [3b].

The rhodium terpyridine hydride complex can be confirmed by ¹ H NMR. As shown in FIG. 5, when trifluoromethanesulfonic acid is added to an acetonitrile solution of rhodium terpyridine low valence complex [2b], the color of the solution changes to yellow, and it is derived from rhodium-hydride in the hydride region by ¹ H NMR. Possible peaks can be confirmed.

The peak of the hydride group is considered to be derived from the rhodium-hydride group because it is split into doublets by coupling with rhodium monovalent (nuclear spin 1/2). Furthermore, when water is added to the produced rhodium terpyridine hydride complex [2b], the color of the solution changes to green, and the disappearance of the peak of the hydride group can be confirmed. The doublet signal at -16.97 ppm in FIG. 5 is typical for this hydride ligand coordinated to the Rh ^III center carrying 1/2 nuclear spin.

<Rhodium terpyridine binuclear complex>
By oxidation of the rhodium terpyridine low valence complex (M + 2e ⁻ ), a rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) (hereinafter also referred to as [4a]) represented by the following formula (4) is generated.

[In the formula (4), X is _{H 2} O. ]

The rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) is also generated by reductive elimination of hydrogen molecules (H ₂ ) from the rhodium terpyridine hydride complex, as shown in the following reaction formula.

In the formulas (3) and (4), X is CH ₃ CN. Quantitative production of H ₂ by reductive elimination can be determined by GC analysis.

When analyzing the structure of a rhodium terpyridine dinuclear complex, the rhodium terpyridine dinuclear complex [3b] is slowly decomposed and the rhodium terpyridine binuclear complex is subjected to reductive elimination of H ₂ as described later in the Examples. Complex [4b] (CF ₃ SO ₃ ) ₄ can be generated and analyzed by X-ray analysis and ¹ H NMR spectroscopy.

FIG. 6 shows the structure of rhodium terpyridine binuclear complex [4b] (CF ₃ SO ₃ ) ₄ obtained by X-ray analysis. As shown in FIG. 6, the rhodium terpyridine binuclear complex forms a double distorted octahedral structure in which rhodium centers are connected by a metal-metal bond. The Rh1-Rh2 metal-metal bond distance {2.6897 (7) Å} in the rhodium terpyridine binuclear complex is the same as that of 2.624 (1) in [Rh ₂ (CH ₃ CN) ₁₀ ] [BF ₄ ] ₄ . Similar to the distance of Rh-Rh single bond (Dunbar, KRJ. Am. Chem. Soc. 1988, 110, 8247.).

<Rhodium terpyridine peroxo complex>
By reacting the rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) with oxygen (O ₂ ), a rhodium terpyridine peroxo complex (hereinafter also referred to as [5a]) represented by the following formula (5) is obtained. Generate.
[M ₂ + 2e ⁻ ] + O ₂ → [M ₂ O ₂ + 2e ⁻ ]

When analyzing the structure of a rhodium terpyridine peroxo complex, [5b] (CF ₃ SO ₃ ) ₄ which is a crystal of a rhodium terpyridine peroxo complex (hereinafter also referred to as [5b]) in formula (5) where X is CH ₃ CN. Can be structurally analyzed by X-ray analysis and Raman spectroscopy.

FIG. 7 is an ORTEP diagram of rhodium terpyridine peroxo complex [5b] (CF ₃ SO ₃ ) ₄ by X-ray structural analysis. As shown in FIG. 7, the rhodium terpyridine peroxo complex has a distorted octahedron in which the Rh center is linked by a trans μ-1,2-peroxo bridge.

8 (a) is rhodium terpyridine peroxo complex _{[5b] (CF 3 SO 3} ) 4 Raman spectrum, FIG. 8 (b) ^[5b which is labeled with ¹⁸ O] rhodium terpyridine peroxo complex _(CF 3 SO ₃ ) The Raman spectrum of ₄ is shown.

FIGS. 8 (a) and 8 (b) show the Raman spectra of rhodium terpyridine peroxo complex [5b] produced with ¹⁶ O ₂ and ¹⁸ O ₂ , respectively, excited by a 532 nm laser. Moreover, FIG.8 (c) is a difference spectrum between Fig.8 (a) and FIG.8 (b).

As shown in FIG. 8 (c), the Raman spectrum of the rhodium terpyridine peroxo complex [5b] indicates that it has an absorption of 816 cm ⁻¹ attributed to v (OO), and the OO stretch The mode is downshifted to 770 cm ⁻¹ by isotopic substitution of ¹⁸ O instead of ¹⁶ O as predicted by Hooke's law calculation (Nakamoto, K. In Infrared and Raman Spectra of Inorganic and Coordination Compounds). 6th ed .; Wiley: New York, 2008, and references therein.).

The oxidation reaction of the substrate of the present invention includes the following steps A, B, D, E or the following steps A, C, D, E.
(Step A) The rhodium terpyridine aqua complex (M) represented by the following formula (1) is allowed to act on the hydrogen molecule (H ₂ ) to extract electrons from the hydrogen molecule, and represented by the following reaction formula: And a step of holding electrons in the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2):
2H ₂ + 2M → 4H ⁺ +2 [M + 2e ⁻ ]
(Step B) As represented by the following reaction formula, the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2) is reacted with a proton, and represented by the following formula (3). The following formula (4) is obtained by reductive elimination of hydrogen via a rhodium terpyridine hydride complex (MH).
Rhodium terpyridine binuclear complex _(M 2 + 2e represented by) ^-) step to produce a ^{2 [M + 2e -] +} 2H + → 2 [MH] → H 2 + [M 2 + 2e -]
(Step C) As represented by the following reaction formula, rhodium terpyridine represented by the following formula (4) is obtained by oxidation of the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2). Step of generating a binuclear complex (M ₂ + 2e ⁻ ) 2 [M + 2e ⁻ ] → 2e ⁻ + [M ₂ + 2e ⁻ ]
(Step D) As represented by the following reaction formula, the rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) is reacted with oxygen (O ₂ ), and the following formula ( 5) Step of producing a rhodium terpyridine peroxo complex represented by [M ₂ + 2e ⁻ ] + O ₂ → [M ₂ O ₂ + 2e ⁻ ]
(Step E) As represented by the following reaction formula, the rhodium terpyridine peroxo complex (M ₂ O ₂ + 2e ⁻ ) represented by the following formula (5) is reacted with the substrate (Q) to oxidize the substrate. Process [M ₂ O ₂ + 2e ⁻ ] + Q + 2H ⁺ + H ₂ O → 2M + QO

  As shown in the following reaction formula, the oxidation reaction of the substrate of the present invention is performed in step A under hydrogen, and steps C to E are performed in oxygen. As described above, since the oxidation reaction of the substrate of the present invention is a reaction system in which hydrogen and oxygen, which are reducing agents, are separately introduced into the system, simple oxidation of the reducing agent (hydrogen) is prevented and there is a risk of explosion. Can be avoided.

In the formula (1), X and Y are each H ₂ O or OH ^— . In the formula (2) ~ (5), X is _{H 2} O. Hereinafter, each process will be described in detail.

(Process A) The process of producing | generating a rhodium terpyridine low valence complex Process A, as represented by the following reaction formula, the rhodium terpyridine aqua complex (M) represented by the following formula (1) and a hydrogen molecule ( H ₂ ), the electrons are extracted from the hydrogen molecules, and as represented by the following reaction formula, electrons are transferred to the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2). This is a step of holding.
2H ₂ + 2M → 4H ⁺ +2 [M + 2e ⁻ ]

  In the formulas (1) and (2), X and Y have the same meaning as described above.

  In step A, hydrogen is introduced into the system and reacted. The reaction time in Step A is preferably 0.5 to 12 hours, the reaction temperature is preferably 15 to 35 ° C., and the reaction pressure is preferably 0.1 to 0.8 MPa.

(Step B) Step of forming a rhodium terpyridine binuclear complex via a rhodium terpyridine hydride complex Step B is a rhodium terpyridine low compound represented by the following formula (2) as represented by the following reaction formula. By reacting protons with the valence complex (M + 2e ⁻ ), it is represented by the following formula (4) by reductive elimination of hydrogen via the rhodium terpyridine hydride complex (MH) represented by the following formula (3). This is a step of producing a rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ).
2 [M + 2e ⁻ ] + 2H ⁺ → 2 [MH] → H ₂ + [M ₂ + 2e ⁻ ]

  In the formulas (2), (3) and (4), X has the same meaning as described above.

(Step C) Step of producing a rhodium terpyridine binuclear complex Step C is an oxidation of a rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2) as represented by the following reaction formula. Is a step of producing a rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4).
2 [M + 2e ⁻ ] → 2e ⁻ + [M ₂ + 2e ⁻ ]

  In formulas (2) and (4), X has the same meaning as described above.

(Step D) Step of producing a rhodium terpyridine peroxo complex Step D is a rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) and oxygen as represented by the following reaction formula ^: This is a step of reacting (O ₂ ) to reductively activate oxygen to produce a rhodium terpyridine peroxo complex represented by the following formula (5).
[M ₂ + 2e ⁻ ] + O ₂ → [M ₂ O ₂ + 2e ⁻ ]

  In the formulas (4) and (5), X has the same meaning as described above.

(Step E) Step of oxidizing substrate As shown in the following reaction formula, in step E, a rhodium terpyridine peroxo complex (M ₂ O ₂ + 2e ⁻ ) represented by the following formula (5) is converted into a substrate (Q). The step of oxidizing the substrate by reacting with [M ₂ O ₂ + 2e ⁻ ] + Q + 2H ⁺ + H ₂ O → 2M + QO

  In the formulas (5) and (1), X and Y are as defined above.

  In Steps C to E, oxygen is introduced into the system and reacted. The reaction time in Steps C to E is preferably 1 to 12 hours, the reaction temperature is preferably 15 to 35 ° C., and the reaction pressure is preferably 0.1 to 0.8 MPa.

  The substrate that is the target of the oxidation reaction of the present invention is not particularly limited, but in addition to saturated hydrocarbons, unsaturated hydrocarbons, alcohols, ketones, aldehydes, amines, etc., thiols, sulfides Amides and phosphines are preferred, and phosphines are more preferred. Specific examples of the substrate include triphenylphosphine.

  In the method for oxidizing a substrate of the present invention, the substrate is oxidized in Step E, and the starting rhodium terpyridine aqua complex can be obtained. Therefore, according to the method for oxidizing a substrate of the present invention, starting from a rhodium terpyridine aqua complex, hydrogen is added in Step A and oxygen is added in Steps C to E to reductively activate oxygen. The substrate can be oxidized continuously.

  Examples of the present invention will be specifically described below, but the present invention is not limited to these.

(Materials and methods)
All experiments were performed under N ₂ or Ar atmosphere by using standard Schlenk techniques and glove boxes.

CH ₃ CN was distilled over CaH ₂ before use.

Rh ^III (terpy) Cl ₃ was prepared by the method described in the literature (Inorg. Chem., 1998, 37, 5733-5742).

H ₂ gas was purchased from Taiyo Toyo Oxygen Corporation. D ₂ O (99.9% D) was purchased from Cambridge Isotope Laboratories, Inc., and H ₂ O was purchased from Wako Pure Chemical Industries, Ltd .; these were used without further purification.

・¹ H NMR spectrum
¹ H NMR spectrum was measured with a JEOL JNM-AL300 spectrometer. The ¹ H chemical shift is 3- (trimethylsilyl) _{propionic-2,2,3,3-d 4} acid sodium salt (TSP, 0.00 ppm) and tetramethylsilane (TMS, 0.00 ppm) as the reference.

And infrared spectrum of the solid compound contained in the infrared spectrum in KBr disc measured the region from 400 using a standard definition ^{2 cm -1} at 25 ° C. until 4000 cm ^-1 in Thermo Nicolet NEXUS6700FR-IR instrument.

Raman spectrum The Raman spectrum was measured using a Raman Jasco NRS-3100 spectrometer at 532 nm wavelength excitation.

-UV visible spectrum The UV visible spectrum was measured with a JASCO V-670 UV-Visible-NIR spectrometer (cell length: 1.0 cm) at 25 ° C.

Elemental analysis data Elemental analysis data was obtained with a Perkin Elmer 2400II series CHNS / O analyzer.

X-ray photoelectron spectrum X-ray photoelectron spectrum (XPS) was obtained on a VG Scientific ESCALAB MK II electron spectrometer by using Mg-K _alpha radiation. The binding energy was corrected by assuming that the Cls binding energy of the carbon atom of the ligand in the sample was 284.5 eV (Handbook of X-ray Photoelectron Spectroscopy, Physical Electronics, Inc., Minnesota, 1995).

  In the pH range of 3.0 to 10.0, the pH value of these solutions was determined by a pH meter (model: TOA HM20J) equipped with a pH composite electrode (model: TOA GST-5725C).

  The value of pD was corrected by adding 0.4 to the observed value (pD = pH meter reading + 0.4) (J. Phys. Chem. 1960, 64, p. 632-637).

· X-ray respective crystallographic _{analysis, [1a] (NO 3)} 3 and [1b] _{(NO 3)} by diffusion over time of the ether to ₂ in methanol [1a] _{(NO 3)} 3 and [1b ] X-ray quality crystals of (NO ₃ ) ₂ and CH of [2b] (CF ₃ SO ₃ ), [4b] (CF ₃ SO ₃ ) ₄ , and [5b] (CF ₃ SO ₃ ) ₄ X-ray quality crystals of [2b] (CF ₃ SO ₃ ), [4b] (CF ₃ SO ₃ ) ₄ , and [5b] (CF ₃ SO ₃ ) ₄ by diffusion of ether into the ₃ CN solution over time. Was made.

  The measurement was performed with a Rigaku / MSC Saturn CCD diffractometer equipped with confocal monochromated Mo-Ka radiation (l = 0.7107 mm). Data was collected and processed using the CrystalClear program (Rigaku). All calculations were performed using Molecular Structure Corporation's teXsan crystallography software package.

The crystallographic data for [1b] (NO ₃ ) ₂ , [2b] (CF ₃ SO ₃ ), [4b] (CF ₃ SO ₃ ) ₄ and [5b] (CF ₃ SO ₃ ) ₄ are Cambridge crystals Deposited at the Structure Data Center (CCDC) as CCDC reference numbers 835746, 835747, 835748 and 838749. A copy of these data can be obtained by applying to CCDC (12, Union Road, Cambridge CB2 1EZ, UK).

[Example 1] Synthesis and analysis of rhodium terpyridine aqua complex (1) Rhodium terpyridine aqua complex [Rh ^III (terpy) (H ₂ O) ₃ ] (NO ₃ ) ₃ {[1a] (NO ₃ ) ₃ } Synthesis of Rh ^III (terpy) Cl ₃ (443 mg, 10.0 μmol, terpy = 2,2 ^′ : 6 ^′ , 2 ^″ -terpyridine) and an aqueous solution of AgNO ₃ (51.3 mg, 30.3 μmol) (10 ml The pH of the solution was adjusted to about 2.0) under N ₂ at room temperature for 12 hours and the precipitated AgCl was removed by filtration. Concentration of the solvent yielded a yellow powder of [1a] (NO ₃ ) ₃ , which was dried under vacuum {yield 98% based on Rh ^III (terpy) Cl ₃ }.

¹ H NMR (300 MHz, in D ₂ O, TSP standard, 25 ° C.): δ-8.10-9.20 (m, 11H, terpy).
Anal. Calcd. for [1a] (NO ₃ ) ₃ : C ₁₅ H ₁₇ N ₆ O ₁₂ Rh: C, 31.27; H, 2.97; N, 14.58%.
Found: C, 31.39; H, 2.98; N, 14.42%.

(2) rhodium terpyridine aqua complex ^{_{[Rh III (terpy) (OH}} ) (H 2 O) 2] (NO 3) 2 {[1b] (NO 3) 2} Synthesis of _{[1a] (NO 3) 3} ( Ether (20 ml) was slowly added to a methanol solution (75 ml, 75 mg, 121 μmol) to give yellow crystals of [1b] (NO ₃ ) ₂ . The crystals were collected by filtration and dried under vacuum {67% yield based on [1a] (NO ₃ ) ₃ }.

¹ H NMR (300 MHz, in D ₂ O, TSP standard, 25 ° C.): δ-8.00-9.05 (m, 11H, terpy).
Anal. Calcd. for [1b] (NO ₃ ) ₂ : C ₁₅ H ₁₆ N ₅ O ₉ Rh; C, 35.10; H, 3.14; N, 13.65%.
Found: C, 34.92; H, 3.12; N, 13.61%.

(3) X-ray analysis of rhodium terpyridine aqua complex [1a] The starting complex [Rh ^III (terpy) (OH ₂ ) ₃ ] (NO ₃ ) ₃ {[1a] (NO ₃ ) ₃ } is Rh ^{III in} water. It was synthesized by adding AgNO ₃ to (terpy) Cl ₃ and processing. Recrystallization of [1a] (NO ₃ ) ₃ in methanol with 0.1% by weight nitric acid provided yellow crystals suitable for X-ray analysis.

FIG. 1 shows an ORTEP diagram of [1a] (NO ₃ ) ₃ having a 50% probability ellipse obtained by X-ray analysis. For clarity, terpy counter anion (NO ₃ ), solvent (methanol) and hydrogen atoms are omitted.

  The main interatomic distances (Å) in FIG. 1 are Rh1-N1 = 2.003 (2), Rh1-N2 = 1.922 (2), Rh1-N3 = 2.037 (2), Rh1-O1 = 2.013 (2), Rh1-O2 = 2.049 (2), Rh1-O3 = 2.024 (2).

As shown in FIG. 1, the rhodium terpyridine aqua complex [1a] is based on a Rh ^III center bound to a terpyridine ligand, and includes three aqua ligands (or two aqua ligands depending on pH). And one hydroxo ligand). Also, the Rh atom had a distorted octahedral coordination surrounded by three aqua ligands.

(4) Analysis of pH behavior of rhodium terpyridine aqua complex Rhodium terpyridine aqua complex [1b] is formed by deprotonation of [Rh ^III (terpy) (OH ₂ ) ₃ ] ³⁺ [1a] Deprotonation produced [Rh ^III (terpy) (OH) ₂ (H ₂ O)] ⁺ [1c].

1a continuous deprotonation process, and monitored by pH titration experiments to determine the pK _a value of aqua ligands. The result is shown in FIG. The pH titration experiment of [1a] (NO ₃ ) ₃ was performed at 25 ° C. using 1M NaOH / H ₂ O.

As shown in Figure 3, pK _a value of 1a and 1b were respectively 4.6 and 7.6. These changes are also reversible. Similarly, deprotonation of 1c formed the corresponding trihydroxo complex [Rh ^III (terpy) (OH) ₃ ] [1d] at pH 10.3.

[Example 2] Synthesis and analysis of rhodium terpyridine low valence complex (1) Rhodium terpyridine low valence complex [Rh ^I (terpy) (H ₂ O)] (NO ₃ ) {[2a] (NO ₃ ) The pH of an aqueous solution (3 ml) of [1b] (NO ₃ ) ₂ (6.2 mg, 12.0 μmol) was adjusted to 7.0 by the addition of 0.01 M NaOH / H ₂ O. The resulting solution was reacted with H ₂ (0.1 MPa) at 25 ° C., and the color of the solution changed to a deep blue color within 30 minutes during the reaction. The solvent was concentrated and dried under vacuum {Yield: 98% based on [1b] (NO ₃ ) ₂ }.

Anal. Calcd. for [2a] (NO ₃ ) : C ₁₅ H ₁₃ N ₄ O ₄ Rh: C, 43.29; H, 3.15; N, 13.46%. Found: C, 43.40; H, 3.25; N, 13.63%.

(2) rhodium terpyridine low valent complex ^{_{[Rh I (terpy) (CH}} 3 CN)] (CF 3 SO 3) {[2b] (CF 3 SO 3)} Synthesis of _{[2a] (NO 3) (} 50 0.0 mg, 95.0 μmol) of the solid sample was dissolved in NaOTf (80 mg, 232.5 μmol) in CH ₃ CH (80 mL) to give a purple solution, to which diethyl ether (200 mL) was added. did. The resulting solution was allowed to stand for several days to obtain purple crystals of [2b] (CF ₃ SO ₃ ). The crystals were collected by filtration and dried under vacuum {Yield: 83% based on [2a] (NO ₃ )}.

¹ H NMR (300 MHz, in CD ₃ CN, TMS standard, 25 ° C.): δ-6.50-8.20 (m, 11H, terpy).
Anal. Calcd. _{for [2 b] (CF 3} SO 3): C 18 H 14 N 4 F 3 O 3 RhS: C, 41.08; H, 2.68; N, 10.65; S, 6.09%. Found: C, 40.83; H, 2.38; N, 10.39; S, 6.04%.

(3) X-ray analysis of rhodium terpyridine low valent complex ^{_{[Rh I (terpy) (CH}} 3 CN)] (CF 3 SO 3) {[2b] (CF 3 SO 3)} X -ray quality violet crystals of in acetonitrile, NO ₃ in [2a] (NO ₃₎ ^- was obtained by substituting the ^- counter-anion _CF 3 SO _3.

FIG. 4 shows an ORTEP diagram of [2b] (CF ₃ SO ₃ ) having a 50% probability ellipse obtained by X-ray analysis. In FIG. 4, counter anions (CF ₃ SO ₃ ) and hydrogen atoms are omitted for clarity.

  The main interatomic distances (Å) in FIG. 4 are Rh1-N1 = 2.030 (2), Rh1-N2 = 1.912 (2), Rh1-N3 = 2.020 (2), Rh1-N4 = 2.019 (2).

As shown in FIG. 4, the rhodium ion in the rhodium terpyridine low-valence complex was located at the center of a planar square structure consisting of one terpyridine and one CH ₃ CN ligand.

[Example 3] Synthesis and identification of rhodium terpyridine hydride complex (1) Rhodium terpyridine hydride complex [Rh ^III (terpy) (CH ₃ CN) ₂ (H)] (CF ₃ SO ₃ ) ₂ {[3b] ( Synthesis of CF ₃ SO ₃ ) ₂ } To a solution of [ 2 b] (CF ₃ SO ₃ ) (10.0 mg, 190 μmol) in CH ₃ CN (0.5 ml) was added CF ₃ SO ₃ H (10 μL). The hydride complex [3b] was produced. At that time, the color of the solution immediately changed from dark purple to pale yellow {yield calculated from ¹ H NMR: [2b] 99% based on (CF ₃ SO ₃ ) }.

¹ H NMR (300 MHz, in CD ₃ CN, TMS standard, 25 ° C.): δ-16.97 {d ¹ , J _{Rh. H} = 14.9Hz, 1H, Rh-H}, 7.50-9.00 (m, 11H, terpy).

(2) Identification of rhodium terpyridine hydride complex by ¹ H NMR spectroscopy At 25 ° C. in CD ₃ CN, rhodium terpyridine hydride complex {[ 3 b] (CF ₃ SO ₃ ) ₂ } is analyzed by ¹ H NMR spectroscopy. analyzed. The result is shown in FIG.

The doublet signal at -16.97 ppm in FIG. 3 is typical for a hydride ligand coordinated to the Rh ^III center carrying 1/2 nuclear spin.

[Example 4] Synthesis and analysis of rhodium terpyridine binuclear complex (1) Rhodium terpyridine binuclear complex [Rh ^II ₂ (terpy) ₂ (CH ₃ CN) ₄ ] (CF ₃ SO ₃ ) ₄ {[4b] Synthesis of (CF ₃ SO ₃ ) ₄ } A solution of [3b] (CF ₃ SO ₃ ) ₂ (30 mg, 57.0 μmol) in CH ₃ CN (3 mL) was allowed to stand for several hours. It turned red. Diethyl ether (10 mL) was slowly added to the resulting solution and allowed to stand for several days to obtain red crystals of [4b] (CF ₃ SO ₃ ) ₄ . The crystals were collected by filtration and dried under vacuum {Isolated yield: 90% based on [3b] (CF ₃ SO ₃ ) ₂ }.

¹ H NMR (300 MHz, in CD ₃ CN, TMS standard, 25 ° C.): 7.50-9.00 (m, 22H, terpy).
Anal. Cald. for [4b] (CF ₃ SO ₃ ) ₄ • CH ₃ CN: C ₄₄ H ₃₇ F ₁₂ N ₁₁ O ₁₂ Rh ₂ S ₄ : C, 35.86; H, 2.53; N, 10.45; S 8.70%.
Found: C, 35.94; H, 2.54; N, 10.36; S, 8.83%.

(2) X-ray analysis of rhodium terpyridine binuclear complex [4b] X-ray of [4b] (CF ₃ SO ₃ ) ₄ by slowly diffusing ether in a CH ₃ CN solution of (CF ₃ SO ₃ ) ₄ Quality red crystals were obtained. FIG. 6 shows an ORTEP diagram of [4b] (CF ₃ SO ₃ ) ₄ having a 50% probability ellipse obtained by X-ray analysis. In FIG. 6, the counter anion (CF ₃ SO ₃ ), the solvent (CH ₃ CN), and the hydrogen atom are omitted for clarity.

  The main interatomic distances (Å) in FIG. 5 are Rh1-Rh2 = 2.6897 (7), Rh1-N1 = 2.52 (2), Rh1-N2 = 1.943 (2), Rh1-N3 = 2.051 (2), Rh1-N4 = 2.025 (2), Rh1-Ni5 = 2.170 (3), Rh2-N6 = 2.056 (2), Rh2-N7 = 1.935 (2) Rh2-N8 = 2.048 (2), Rh2-N9 = 2.046 (2), Rh2-N10 = 2.203 (3).

  As shown in FIG. 5, the rhodium terpyridine binuclear complex [4b] formed a double distorted octahedral structure in which the Rh center was linked by a metal-metal bond.

The rhodium terpyridine binuclear complex [4b] is also produced by reacting the rhodium low valence complex [2b] with 0.25 equivalent of O ₂ . From this result, it was found that the use of such a limited amount of O ₂ prevented the subsequent oxidation to the rhodium terpyridine peroxo complex [5b] and stopped the reaction cycle at an early stage.

[Example 5] Synthesis and analysis of rhodium terpyridine peroxo complex (1) Rhodium terpyridine peroxo complex [Rh ^III ₂ (terpy) ₂ (CH ₃ CN) ₄ (μ-η ¹ : η ¹ -O ₂ )] ( _{CF 3 SO 3) 4 {[} 5b] (CF 3 SO 3) 4} synthesis _{[4b] (CF 3 SO 3} ) 4 (30mg, CH 3 CN solution (3 mL) _{O 2} molecules of 57.0μ mol) The color of the solution immediately changed from red to reddish brown. Diethyl ether (10 mL) was slowly added to the resulting solution and allowed to stand for several days to obtain red crystals of [5b] (CF ₃ SO ₃ ) ₄ . The crystals were collected by filtration and dried under vacuum {Isolated yield: 40% based on [4b] (CF ₃ SO ₃ ) ₄ }.

¹ H NMR (300 MHz, in CD ₃ CN, TMS standard, 25 ° C.): 7.60-8.70 (m, 22H, terpy).
Anal. Calcd. for [5b] (CF ₃ SO ₃ ) ₄ · 2CH ₃ CN: C ₄₆ H ₄₀ F ₁₂ N ₁₂ O ₁₄ Rh ₂ S ₄ : C, 35.72; H, 2.61; N, 10.87: S , 8.29%.
Found: C, 35.57; H, 2.70; N, 10.68; S, 8.25%.

(2) Time-dependent change by UV-vis spectrum during reaction of rhodium terpyridine low valence complex [2b] with oxygen.
Since rhodium terpyridine low valence complex [2b] has low solubility in water, rhodium terpyridine low valence complex [2b] is dissolved in acetonitrile, reacted with oxygen, and the change with time is measured by UV-vis. Confirmed by spectrum.

  Spectral measurements were made in a quartz cell fitted with a septum cap, while stirring a 10 μM rhodium terpyridine low valence complex [2b] acetonitrile solution with a 25 G needle in the septum and gradually reacting with oxygen. The color change of the solution was measured at 150 second intervals using UV-vis.

  The result is shown in FIG. As shown in FIG. 9, due to the reaction of the rhodium terpyridine low valence complex [2b] with oxygen, a strong absorption band at 320 nm and a broad band around 400 to 700 nm due to the rhodium terpyridine low valence complex [2b] are obtained. The absorption band decayed, at which point the color of the solution changed from purple to reddish brown.

(3) X-ray analysis of rhodium terpyridine peroxo complex The structure of rhodium terpyridine peroxo complex [5b] (CF ₃ SO ₃ ) ₄ was analyzed by X-ray analysis. FIG. 7 shows an ORTEP diagram of rhodium terpyridine peroxo complex [5b] (CF ₃ SO ₃ ) ₄ having a 50% probability ellipse obtained by X-ray analysis. In FIG. 7, counter anions (CF ₃ SO ₃ ) and hydrogen atoms are omitted for the sake of clarity.

The main interatomic distance (Å) and angle (°) in FIG. 6 are O1-O1 ^* = 1.456 (4), Rh1-O1 = 1.951 (2), Rh1-N1 = 2.402 (2 ), Rh1-N2 = 1.936 (2), Rh1-N3 = 2.048 (3), Rh1-N4 = 2.050 (2), Rh1-N5 = 2.043 (2), Rh1-O1- O1 ^* = 108.3 (2).

As shown in FIG. 6, the rhodium terpyridine peroxo complex [5b] (CF ₃ SO ₃ ) ₄ had a distorted octahedron in which the Rh center was linked by a trans μ-1,2-peroxo bridge.

The O1-O1 ^* bond distance (1.456 (4) Å) in the rhodium terpyridine peroxo complex [5b] (CF ₃ SO ₃ ) ₄ is the value usually mentioned for the superoxide species (O ₂ ⁻ ). It was a value closer to 1.49%, which is the value usually referred to for the peroxide species (O ₂ ²⁻ ), rather than 1.28% [(a) Jones, R .; D. Somerville, D .; A. Basolo, F .; Chem. Rev. 1979, 79, 139-179. (B) Niederhofer, E .; C. Timmons, J .; H. Martell, A .; E. Chem Rev. 1984, 84, p. 137-203. ].

Also, the Rh1-O1 ^* angle, 108.3 (2) °, in the rhodium terpyridine peroxo complex [5b] (CF ₃ SO ₃ ) ₄ was smaller than the values observed for other peroxo complexes (Mishra, B. K .; Sathyamurthy, NJ Phys. Chem. A 2005, 109, p.6-8.).

  From the results of Raman analysis described below, this short bond length for the peroxo-bridged ligand was considered to be a result of the π-π affinity interaction between the terpyridine ligands. This was also concluded by the fact that the terpyridine ligands were twisted together.

(4) Analysis of rhodium terpyridine peroxo complex by Raman spectroscopy The structure of rhodium terpyridine peroxo complex [5b] (CF ₃ SO ₃ ) ₄ was analyzed by Raman spectroscopy. The results are shown in FIGS.

FIG. 8A shows the Raman spectrum of rhodium terpyridine peroxo complex [5b] (CF ₃ SO ₃ ) ₄ , and FIG. 8B shows the rhodium terpyridine peroxo complex [5b labeled with ¹⁸ O] (CF ₃ SO ₃ ) The Raman spectrum of ₄ is shown.

FIGS. 8 (a) and 8 (b) describe the Raman spectra of the rhodium terpyridine peroxo complex [5b] produced with ¹⁶ O ₂ and ¹⁸ O ₂ respectively, excited by a 532 nm laser. FIG. 8 (c) is a difference spectrum between FIG. 8 (a) and FIG. 8 (b).

As shown in FIG. 8 (c), the Raman spectrum of the rhodium terpyridine peroxo complex [5b] indicates that it has an absorption of 816 cm ⁻¹ attributed to v (OO), and the OO stretch The mode was downshifted to 770 cm ⁻¹ by isotope substitution of ¹⁸ O instead of ¹⁶ O as predicted by Hooke's law calculations.

Example 6 rhodium terpyridine peroxo complex rhodium terpyridine low valent complex oxide N ₂ vials under an atmosphere of substrate _{[2a] (NO 3) (} 5.0mg, 3.0μ mol), _PPh 3 (2 .6 mg, 10.0 μmol) and H ₂ O (3 mL) / CDCl ₃ (1 mL) two-phase solvent were added, and a stir bar was added, followed by capping with a septum. The gas phase was replaced with O ₂ and stirred at 25 ° C. for 2 hours.

The resulting product was extracted with CDCl ₃ and analyzed by ¹ H NMR. As a result, the yield of OPPh ₃ was 98% based on the rhodium terpyridine low valence complex [2a] (NO ₃ ).

[Comparative Example 1] Oxidation reaction of triphenylphosphine using hydrogen / oxygen mixed gas Hydrogen / oxygen mixed gas (H ₂₎ prepared by using rhodium terpyridine triaqua complex 1a as a starting complex and adjusting the mixing ratio of hydrogen outside the explosion range. : 1.3%, O ₂ : 1.7%, remaining N ₂ ) was used to confirm whether the oxidation reaction of triphenylphosphine proceeds catalytically. The reaction was performed as shown in the scheme shown in FIG.

An aqueous solution (4 mM, 3 mL, pH 7.0) of rhodium terpyridine aqua complex [1a] and a chloroform solution of triphenylphosphine (10 mM, 1 mL) were placed in a pressure-resistant container having a volume of 50 mL, and the inside of the container was replaced with a mixed gas. After stirring this mixed solution at room temperature for 12 hours, the chloroform phase was extracted, and the amount of triphenylphosphine oxide (OPPh ₃ ) as an oxidation product was confirmed by ¹ H NMR.

As a result, the amount of OPPh ₃ produced in the solution after the reaction is not different from that before the reaction and the blank (no catalyst / reaction in mixed gas atmosphere, OPPh ₃ ≦ 1%). Then, it was found that the oxidation reaction of OPPh ₃ does not proceed.

[Example 7] Continuous oxidation reaction of triphenylphosphine Using triaqua complex 1a as a starting complex, an oxidation reaction of PPh ₃ was continuously carried out to confirm whether the catalytic activity was not lowered. The reaction was performed as shown in the scheme shown in FIG.

The reaction was initially Toriakua complex 1a (4 mM, 3 mL, pH 7.0) and subjected to reaction with hydrogen (0.1 MPa) (6 hours), to produce a low valent complex 2 a. After purging hydrogen, chloroform solution of PPh ₃ complexes 1a equimolar amounts (7.5 mM, 1 mL) was added a stirring oxygen (0.1 MPa) 2 hours under atmosphere, the PPh ₃ rhodium terpolymer by the following reaction formula OPPh ₃ was generated by oxidation with pyridine peroxo complex [5b].

After the reaction, the chloroform phase was extracted, and the production of OPPh ₃ was confirmed by ¹ H NMR. The aqueous phase containing the complex was deaerated to remove dissolved oxygen, and the reaction of hydrogen → oxygen / substrate was repeated as shown in FIG.

  The yield was calculated based on rhodium terpyridine peroxo complex [5a] capable of acting as a two-electron oxidant. The result is shown in FIG.

As shown in FIG. 12, the rhodium terpyridine peroxo complex [5a] could be reused at least four times. That is, when H ₂ , O ₂ and additional substrate were added in this order after the reaction, the reaction cycle was resumed.

The rhodium terpyridine peroxo complex [5a] was slowly inactivated. The overall yield of OPPh ₃ was not 400% on its fourth use. This is because the yield of each cycle was 84-90% based on rhodium terpyridine peroxo complex [5a], which is usually considered to be a two-electron oxidant.

  From this result, according to the method for oxidizing a substrate of the present invention, by using a rhodium terpyridine aqua complex and hydrogen as a reducing agent, oxygen molecules are reductively activated in a homogeneous system, and the substrate is converted by the oxygen molecules. It has been found that it can be oxidized continuously.

Claims (11)

A method for oxidizing a substrate comprising the following steps A, B, D, E or the following steps A, C, D, E.
(Step A) The rhodium terpyridine aqua complex (M) represented by the following formula (1) is allowed to act on the hydrogen molecule (H ₂ ) to extract electrons from the hydrogen molecule, and represented by the following reaction formula: And a step of holding electrons in the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2):
2H ₂ + 2M → 4H ⁺ +2 [M + 2e ⁻ ]
(Step B) As represented by the following reaction formula, the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2) is reacted with a proton, and represented by the following formula (3). Step 2 [M + 2e ⁻ ] of producing a rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) by reductive elimination of hydrogen via a rhodium terpyridine hydride complex (MH) + 2H ⁺ → 2 [MH] → H ₂ + [M ₂ + 2e ⁻ ]
(Step C) As represented by the following reaction formula, rhodium terpyridine represented by the following formula (4) is obtained by oxidation of the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2). Step of generating a binuclear complex (M ₂ + 2e ⁻ ) 2 [M + 2e ⁻ ] → 2e ⁻ + [M ₂ + 2e ⁻ ]
(Step D) As represented by the following reaction formula, the rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) is reacted with oxygen (O ₂ ), and the following formula ( 5) Step of producing a rhodium terpyridine peroxo complex represented by [M ₂ + 2e ⁻ ] + O ₂ → [M ₂ O ₂ + 2e ⁻ ]
(Step E) As represented by the following reaction formula, the rhodium terpyridine peroxo complex (M ₂ O ₂ + 2e ⁻ ) represented by the following formula (5) is reacted with the substrate (Q) to oxidize the substrate. Process
[M ₂ O ₂ + 2e ⁻ ] + Q + 2H ⁺ + H ₂ O → 2M + QO
[In the above reaction formula, Q is triphenylphosphine. ]

[In the formula (1), X and Y are each H ₂ O or OH ⁻ (except that both X and Y are OH ⁻ ) . ]

[In the formula (2), X is _{H 2} O. ]

[In the formula (3), X is _{H 2} O. ]

[In the formula (4), X is _{H 2} O. ]

[In formula (5), X is _{H 2} O. ] A rhodium terpyridine aqua complex (M) represented by the following formula (1) used in the oxidation method according to claim 1.

[In the formula (1), X and Y are each H ₂ O or OH ⁻ (except that both X and Y are OH ⁻ ) . ] A rhodium terpyridine low-valence complex (M ₂ + 2e ⁻ ) represented by the following formula (2) used in the oxidation method according to claim 1.

[In the formula (2), X is _{H 2} O. ] The rhodium terpyridine hydride complex (MH) represented by following formula (3) used for the oxidation method of Claim 1.

[In the formula (3), X is _{H 2} O. ] A rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) used in the oxidation reaction according to claim 1.

[In the formula (4), X is _{H 2} O. ] A rhodium terpyridine peroxo complex (M ₂ O ₂ + 2e ⁻ ) represented by the following formula (5) used in the oxidation method according to claim 1.

[In formula (5), X is _{H 2} O. ] The rhodium terpyridine aqua complex (M) represented by the following formula (1) is allowed to act on the hydrogen molecule (H ₂ ), and electrons are extracted from the hydrogen molecule. A method of holding electrons in the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by (2).
2H ₂ + 2M → 4H ⁺ +2 [M + 2e ⁻ ]

[In the formula (1), X and Y are each H ₂ O or OH ⁻ (except that both X and Y are OH ⁻ ) . ]

[In the formula (2), X is _{H 2} O. ] As represented by the following reaction formula, a rhodium terpyridine represented by the following formula (3) is obtained by reacting a proton with the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2). A method for producing a rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) by reductive elimination of hydrogen via a hydride complex (MH).
2 [M + 2e ⁻ ] + 2H ⁺ → 2 [MH] → H ₂ + [M ₂ + 2e ⁻ ]

[In the formula (2), X is _{H 2} O. ]

[In the formula (3), X is _{H 2} O. ]

[In the formula (4), X is _{H 2} O. ] As represented by the following reaction formula, the rhodium terpyridine binuclear complex represented by the following formula (4) (O) is oxidized by oxidation of the rhodium terpyridine low valence complex (M + 2e ⁻ ) represented by the following formula (2) ( M ₂ + 2e ⁻ ).
2 [M + 2e ⁻ ] → 2e ⁻ + [M ₂ + 2e ⁻ ]

[In the formula (2), X is _{H 2} O. ]

[In the formula (4), X is _{H 2} O. ] As represented by the following reaction formula, the rhodium terpyridine binuclear complex (M ₂ + 2e ⁻ ) represented by the following formula (4) is reacted with oxygen (O ₂ ), and is represented by the following formula (5). To produce a rhodium terpyridine peroxo complex.
[M ₂ + 2e ⁻ ] + O ₂ → [M ₂ O ₂ + 2e ⁻ ]

[In the formula (4), X is _{H 2} O. ]

[In formula (5), X is _{H 2} O. ] A method of oxidizing a substrate by reacting a rhodium terpyridine peroxo complex (M ₂ O ₂ + 2e ⁻ ) represented by the following formula (5) with a substrate (Q) as represented by the following reaction formula.
[M ₂ O ₂ + 2e ⁻ ] + Q + 2H ⁺ + H ₂ O → 2M + QO
[In the above reaction formula, Q is triphenylphosphine. ]

[In formula (5), X is _{H 2} O. ]

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