EP1133502A1

EP1133502A1 - Method of producing ruthenium complexes

Info

Publication number: EP1133502A1
Application number: EP99959310A
Authority: EP
Inventors: Peter Schwab; Michael Schulz; Justin Wolf; Helmut Werner
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1998-11-27
Filing date: 1999-11-23
Publication date: 2001-09-19
Also published as: CA2352377A1; KR20010080598A; AU1653400A; JP2002531461A; CN1331696A; ID29912A; DE19854869A1; WO2000032614A1

Abstract

The invention relates to a method of producing ruthenium complexes of general formula (I): RuX2(=CH-CH2R)L1L2, wherein X is an anionic ligand, R is hydrogen or an optionally substituted C¿1-20? alkyl radical or C6-20 aryl radical, and L?1 and L2¿ independently are neutral electron-donor ligands. Said ruthenium complexes are produced by a) reacting RuX¿3? with a diene in a solvent on the basis of one or several aliphatic secondary alcohols in the presence of a reducing adjuvant, reacting said mixture with L?1 and L2¿ in the presence of at least one coordinating weak base and hydrogen and without isolating any intermediates, b) reacting the mixture with compounds of general formula (II): R-C≡CH, wherein R has the meaning indicated above, in the presence of a soluble chloride source.

Description

Process for the preparation of ruthenium complexes

The invention relates to processes for the preparation of ruthenium complexes which can be used, for example, as catalysts in metathesis reactions.

In its simplest form, olefin metathesis (disproportionation) involves a reversible, metal-catalyzed transalkylidation of olefins by breaking and reforming carbon-carbon double bonds. In the case of the metathesis of acyclic olefins, a distinction is made, for example, between a self-metathesis, in which an olefin changes into a mixture of two olefins of different molar masses (e.g. conversion of propene to ethene and 2-butene), and cross- or co-metathesis, the one Describes conversion of two different olefins (for example, from propene with 1-butene to ethene and 2-pentene). Other fields of application for olefin metathesis include syntheses of unsaturated polymers by ring-opening metathesis polymerization (ROMP) of cyclic olefins and acyclic diene metathesis polymerization (ADMET) of α, ω-dienes. More recent applications relate to the selective ring opening of cyclic olefins with acyclic olefins, as well as ring closure reactions (RCM), with which - preferably from ω-dienes - unsaturated rings of different ring sizes can be produced.

In principle, homogeneous and heterogeneous transition metal compounds, in particular ruthenium compounds, are suitable as catalysts for metathesis reactions.

Heterogeneous catalysts, for example molybdenum, tungsten or rhenium oxides on inorganic oxidic supports, are notable for high activity and regenerability in reactions of nonfunctionalized olefins, However, when using functionalized olefins, such as methyl oleate,

Increased activity can often be pretreated with an alkylating agent. Olefins with protic functional groups (such as hydroxyl groups, carboxyl groups or amino groups) lead to the spontaneous deactivation of the heterogeneous act.

In recent years, efforts have been made to produce homogeneous catalysts which are stable in protic medium and in atmospheric oxygen. Special ruthenium alkylidene compounds have found particular interest. Such complexes and processes for their preparation are known.

WO 93/20111 describes ruthenium and osmium metal carbene complexes for olefin metathesis polymerization. The complexes have the structure RuX ₂ (= CH-CH = CR ₂ ) L2. Triphenylphosphine and substituted triphenylphosphine are used as ligands L. They are produced, for example, by reacting RuCl ₂ (PPh ₃ ) ₃ with suitable disubstituted cyclopropenes as carbene precursors. However, the synthesis of cyclopropene derivatives is multi-stage and of little economic interest.

Similar implementations are described in WO 96/04289. Methods for olefin metathesis polymerization are also given.

The use of such catalysts for the peroxide crosslinking of ROMP polymers is described in WO 97/03096.

WO 97/06185 likewise describes metathesis catalysts which are based on ruthenium metal-carbene complexes. In addition to the process described above, they can also be prepared by reacting RuCl ₂ (PPli ₃ ) ₃ with diazoalkanes. However, handling diazoalkanes poses a security risk, especially when the process is carried out on a technical scale.

In addition, the organometallic starting materials used have the formula RuCl ₂ (PPh ₃ ) ₃ using a large excess of triphenylphosphine RUCI ₃ 3 H ₂ O can be produced. In the catalyst synthesis itself, PPlij ligands are then lost again after ligand exchange. The carbene precursors used require multi-stage syntheses and are not stable indefinitely.

Organometallics 1996, 15, 1960 to 1962 describes a process for the preparation of ruthenium complexes in which polymeric [RuCl ₂ (cyclooctadiene)] _{x is} reacted in i-propanol in the presence of phosphine with hydrogen and then with 1-alkynes. This eliminates the need for phosphine exchange. An undefined mixture of products is obtained. In addition, long reaction times are required starting from a polymeric starting material. The cyclooctadiene contained in the organometallic starting material does not contribute to the reaction and is lost.

In J. Chem. Soc. Commun. 1997, 1733 to 1734 a synthesis of the methylene complex RuCl ₂ (= CH ₂ ) (PCy ₃ ) _{2 is} described, which starts from dichloromethane and the ruthenium polyhydride RuH ₂ (H ₂ ) ₂ (PCy ₃ ) ₂ . However, the ruthenium-polyhydride complex is difficult to access. Long reaction times are also required.

The known synthetic routes for the production of metathesis catalysts of the type are uneconomical for the reasons mentioned.

DE-A198 00 934, which is older and not prepublished, describes a process for the preparation of ruthenium complexes of the RuX ₂ (= CH-CH ₂ R) LL type, in which RUX _{3 is} in an inert solvent in the presence of a reducing agent and of hydrogen and then is reacted with alkyne compounds.

The object of the present invention is to provide a process for the production of ruthenium-alkylidene complexes of the RuX ₂ (= CH-CH R) L ^l L ^{2 type} , which can be carried out in a rapid and atomically economical implementation, starting from easily accessible starting materials, without ligand exchange and without ligands - shot in high yield leads to the desired products. In addition, the process should do without complex workup steps, should be able to be carried out under mild reaction conditions and should also be inexpensive.

The object is achieved according to the invention by a process for the preparation of ruthenium complexes of the general formula I.

in the

X is an anionic ligand,

R is hydrogen or an, optionally substituted, -C _-2 o-alkyl radical or C ₆ - ₂ o-aryl radical, and

1 "7

L and L are independently neutral electron donor ligands,

by

a) reaction of RuX ^ with a diene in a solvent based on one or more aliphatic secondary alcohols in the presence or absence of a reducing aid, and

1 then with L and L in the presence of at least one coordinating weak base and of hydrogen and without

Isolation of intermediates b) subsequent reaction with compounds of the general formula II

R-C-CH (II)

in which R has the meaning given above, in the presence of a soluble chloride source. It was found that the above ruthenium complexes directly from RÜX ₃ , preferably RuCl ₃ -3 (H ₂ θ), by simple reaction with dienes and then with ligands L ¹ and L ² . Hydrogen and terminal alkynes of the general formula II, preferably in the presence of reduction auxiliaries without isolation of intermediates, can be obtained in very good yields. The ruthenium complexes contain no vinyl substituents on the carbene carbon atom. The raw materials are inexpensive to manufacture and readily available.

First, RUX _{3 is} reacted with the diene and then with the ligands L ¹ and L "in a solvent based on one or more aliphatic secondary alcohols, preferably in the presence of a reducing aid. At least one coordinating weak base and hydrogen. The solvent is based on one or more aliphatic secondary alcohols These alcohols preferably have 3 to 10, particularly preferably 3 to 6, carbon atoms, isopropanol, 2-butanol, cyclohexanol or a mixture thereof are particularly preferred, and isopropanol is particularly preferred.

The coordinating weak base is a secondary or, preferably, a tertiary amine. An example of a secondary amine is dicyclohexylamine. Tertiary aliphatic amines, in particular trialkylamines, in which the alkyl radicals have 1 to 12, preferably 2 to 6, carbon atoms are particularly preferred. Triethylamine is particularly preferably used. The coordinating weak base, in particular triethylamine, is preferably used in at least a stoichiometric amount, based on RuX. The reaction mixture is preferably pretreated with the coordinating weak base before adding the ligand L.

Before the addition of the ligand L, the reaction mixture is reacted with a diene, preferably C ₄ to cio diene, in particular isoprene, preferably in the presence of a reducing aid, in particular an alkali metal or alkaline earth metal carbonate. Sodium carbonate and / or calcium carbonate are particularly preferably used as alkali or alkaline earth carbonate. It is Molar ratio of diene to RÜX ₃ preferably at least 5: 1 and the molar ratio of alkali and / or alkaline earth carbonate to RUX ₃ 0.1 to 1, particularly preferably about 0.5.

The reduction with hydrogen takes place in the presence of a coordinating weak base, preferably a secondary or tertiary amine. Triethylamine is particularly preferably used.

The reaction mixture is reacted with a 1-alkyne in the presence of a soluble chloride source, in particular an alkaline earth metal chloride. Magnesium chloride is particularly preferably used.

The temperature in this reaction step (a) is preferably 0 to 100 ° C., particularly preferably 20 to 80 ° C., in particular 40 to 60 ° C. The pressure is preferably 0.1 to 100 bar, particularly preferably 0.5 to 5 bar, in particular 0.8 to 1.5 bar. The reaction takes place for a period of preferably 10 minutes to 100 hours, particularly preferably one hour to 10 hours. The molar ratio of ligands L ¹ and L ^{2 taken} together to the ruthenium salt used is preferably 2 to 20: 1, particularly preferably 2 to 5: 1. After the reaction in step (a), the reaction mixture is preferably reacted with a 1-alkyne at a temperature in the range from -80 to 100.degree. C., particularly preferably from -40 to 50.degree. C., in particular from -30 to 20.degree. The molar ratio of the ruthenium salt originally used to 1-alkyne is preferably 1: 1 to 1:10. The reaction is preferably carried out at a pressure of 0.1 to 10 bar, particularly preferably 0.8 to 1.5 bar, in particular 1 to 1.4 bar for a period of preferably 30 seconds to 10 hours, particularly preferably one minute to one Hour.

To prepare the complexes of the general formula I, isolation of the intermediate from step (a) is not necessary, but is possible.

The reaction mixture obtained is preferably worked up by filtering off the precipitated solid, washing and drying. In the ruthenium complexes of the general formula I, X is a monodentate anionic ligand, for example halogen, pseudohalogen, carboxylate, diketonate. X particularly preferably denotes halogen, in particular bromine or chlorine, especially chlorine. RuCl ₃ -3H ₂ O is particularly preferably used in the reaction.

L and L are neutral electron donor ligands. Examples include amines, phosphines, arsanes and stibans, preferably phosphines. L and L are particularly preferably selected from phosphines of the general formula III

PR ^! R ² R ³ (III)

in which R ¹ and R ^{2 are} independently phenyl radicals or organic sterically hindering radicals and R ^{3 is} hydrogen, an optionally substituted C ₂₀ alkyl radical or C _6-20 aryl radical or as R ^{1 is} defined. “Sterically hindering radical” is understood to mean those radicals which have a spatially demanding structure. Examples of such radicals are i-propyl, tert-butyl, cyclopentyl, cyclohexyl, phenyl or menthyl. A cyclohexyl radical is preferably used as the sterically preventing radical. Particularly all three radicals R ¹ , R ² and R ^{3 are} preferably sterically hindering radicals or phenyl radicals, in particular cyclohexyl radicals. The radicals R, R and R can in each case carry suitable substituents. Examples of such substituents are C ₆ alkyl radicals, preferably C ₃ - alkyl, Cι- -Fluoralkylreste _3, halogen atoms, nitro groups, amino groups, ester, and acid functions, -OH, Cι _-6 -.. alkoxy groups or sulfonate groups are preferably the radicals substituted not L ¹ and L ² are preferably in a molar ratio of 1 5 to 4, particularly preferably about 2, based on RÜX ₃ , used.

The radical R is hydrogen or an optionally substituted C _2-2 , preferably C ₆ alkyl or C ₆ . ₂₀ -, preferably Cö-s-aryl radical. What has been said above applies to the substituents. Particularly preferred as the ruthenium complex of the general formula I are the complexes RuCl ₂ (= ^: CH-CH ₃ ) (PCy ₃ ) and RuCl ₂ ( ^: = CH-CH2-Ph) (PCy ₃ ) ₂ where Cy is a cyclohexyl radical and Ph is a phenyl radical mean. In a preferred embodiment, RUCI ₃ XH ₂ O with Na ₂ CO ₃ or CaCO ₃ in isopropanol, 2-butanol or cyclohexanol is introduced in a one-pot reaction (under an inert gas atmosphere) and heated after addition of isoprene. After excess isoprene has been removed in vacuo, triethylamine and stoichiometric amounts of phosphine, in a preferred embodiment two equivalents of tricyclohexylphosphine, are added to the reaction mixture. In a hydrogen atmosphere of 0.1 bar to 100 bar, preferably 0.5 to 5 bar, particularly preferably 0.8 to 1.5 bar, the mixture is then stirred for 10 minutes to 100 hours at temperatures from 0 ° C. to 100 ° C. and then MgCl ₂ x6H ₂ O added. The reaction mixture thus obtained is then at a temperature of -80 ° C to 100 ° C, preferably at -40 ° C and 50 ° C in a molar ratio of 1: 1 to 1:10, based on the ruthenium chloride used, with a 1 -alkyne the composition HC≡CR at pressures of 0.1 to 10 bar, preferably at 0.8 to 1.5 bar, continuously implemented over a period of 30 to 180 min. The solid which precipitates out of the solution approximately quantitatively is the desired alkylidene complex which, after drying, can be used directly as a highly active metathesis catalyst for all of the metathesis reactions described in the introduction.

As a rule, the entire reaction and workup sequence is complete after 2 to 100 h, preferably after 3 h to 8 h, and gives metathesis catalysts of the RuCl ₂ (= CHCH ₂ R) (PR ' ₃ ) 2 (R = H, alkyl, aryl) in yields of at least 60 to 98% based on RuC ^ and the phosphine used.

Glass or steel containers are generally suitable as reactors, which should, if appropriate, be pressure-stable.

The invention is illustrated by the example. Example:

Synthesis of the ethylidene complex RuCl ₂ (= CHMe) (PCy ₃ ) ₂ :

1.09 g (3.95 mmol) RuCl ₃ -3H ₂ O and 198 mg CaCO ₃ (1.98 mmol) are added under protective gas in 150 ml isopropanol with 4 ml isoprene (40.0 mmol) and the reaction mixture is Heated to 85 ° C in a closed flask for 1 to 2 h, a color change from red to brown-black to orange-red being observed. The heating is removed, the volume of the solution is reduced by approximately 20 to 30 ml and the mixture is stirred for 5 min after the addition of 2 ml of triethylamine (14.4 mmol). 2.24 g of tricyclohexylphosphine (7.99 mmol) are then added. After stirring for 10 minutes, the protective gas is now replaced by hydrogen at a pressure of 0.6 to 0.8 bar and the reaction solution is heated to 65 ° C. for 45 minutes, an orange-yellow suspension having formed after only 15 minutes. After cooling the suspension to room temperature, hydrogen is replaced by protective gas, and after adding 1.60 g (7.87 mmol) of MgCl ₂ x6H ₂ O, 220 ml of acetylene (approx. 4.6 mmol) are continuously added over a period of 90 min. added. After the addition is complete, the suspension is stirred for a further 10 min. A vacuum is briefly applied to remove residual amounts of acetylene. The violet solid which has precipitated out of the solution is filtered off. washed with water and methanol and dried in vacuo.

Yield: 2.85 g (93%)

Claims

claims

1. Process for the preparation of ruthenium complexes of the general formula I

RuX ₂ ( ^: = CH-CH ₂ R) L'L ² (I)

in the

X is an anionic ligand,

R is hydrogen or, optionally substituted, Cι _-20 alkyl or C ₆ a - ₂ o-aryl radical, and

L ¹ and L are independently neutral electron donor ligands,

by

(a) Reaction of RuX ₃ with a diene in a solvent

Base of one or more aliphatic secondary alcohols in the presence or absence of a reducing aid, and then with L and L in the presence of at least one coordinating weak base and of hydrogen and without isolation of intermediates

(b) subsequent reaction with compounds of the general formula II

R-C≡CH (II)

in which R has the meaning given above, in the presence of a soluble chloride source.

2. The method according to claim 1, characterized in that the reaction mixture before the addition of the ligands L ¹ and L ² with a diene in a molar ratio of at least 5: 1, based on RUX ₃ , is added.

3. The method according to claim 1 or 2, characterized in that L ¹ and L ^{2 are} selected from phosphines of the general formula III

PR * R ² R ³ (III)

in which R ¹ and R independently of one another are phenyl radicals or organic sterically hindering radicals and R ^{3 is} hydrogen, an optionally substituted Ci.π-alkyl radical or Cö- _20- aryl radical and / or as defined for R ¹ .

4. The method according to claim 3, characterized in that R ¹ and R ^{2 are} selected from i-propyl, tert-butyl, cyclopentyl, cyclohexyl, phenyl or menthyl.

5. The method according to any one of claims 1 to 4, characterized in that X is halogen.

6. The method according to any one of claims 1 to 5, characterized in that the reaction of RUX ₃ with a diene in the presence of Na ₂ CO ₃ and / or CaCÜ _{3 is} carried out, the molar ratio of Na ₂ CO ₃ and / or CaCO ₃ for RuX _{3 is} 0.1 to 1.

7. The method according to any one of claims 1 to 6, characterized in that the reaction with hydrogen in the presence of a secondary and / or tertiary amine is carried out as a coordinating weak base.

8. The method according to any one of claims 1 to 7, characterized in that the reaction with 1 -alkynes is carried out in the presence of an alkaline earth metal chloride.

9. The method according to any one of claims 1 to 8, characterized in that the reaction in step (a) at a pressure in the range from 0.1 to 100 bar and in step (b) at a pressure in the range from 0.1 to 10 bar is carried out.

10. The method according to any one of claims 1 to 9, characterized in that the reaction in step (a) at a temperature in the range from 0 to 100 ° C and in step (b) at a temperature in the range from -80 to 100 ° C is carried out.

11. The method according to any one of claims 1 to 10, characterized in that the solvent is selected from isopropanol, 2-butanol, cyclohexanol and mixtures thereof.