Method for producing ruthenium complexes

Details Method for producing ruthenium complexes Method for producing ruthenium complexes

2000-05-08

2001-05-15

Nazario-Gonzalez, Porfirio (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Heavy metal containing

C556S136000, C556S137000, C502S155000

Reexamination Certificate

active

06232482

ABSTRACT:

The present invention relates to processes for preparing ruthenium complexes which can be used, for example, as catalysts in metathesis reactions.
In its simplest form, olefin metathesis (disproportionation) is a reversible, metal-catalyzed transalkylidenation of olefins by rupture and re-formation of carbon-carbon double bonds. In the metathesis of acyclic olefins, a distinction is made, for example, between self-metathesis, in which an olefine is converted into a mixture of two olefins of different molar masses (for example conversion of propene into ethene and 2-butene), and cross- or co-metathesis, which describes the reaction of two different olefins (for example of propene with 1-butene to give ethene and 2-pentene). Further application areas of olefin metathesis are syntheses of unsaturated polymers by ring-opening metathesis polymerization (ROMP) of cyclic olefins and the acyclic diene metathesis polymerization (ADMET) of &agr;, &ohgr;-dienes. More recent applications are the selective ring opening of cyclic olefins using acyclic olefins, and also ring closure reactions (RCM) by means of which unsaturated rings of different ring sizes can be produced, preferably from &agr;, &ohgr;-dienes.
Suitable catalysts for metathesis reactions are in principle homogeneous and heterogeneous transition metal compounds, in particular ruthenium compounds.
Heterogeneous catalysts, for example molybdenum oxide, tungsten oxide or rhenium oxide on inorganic oxidic supports, have a high activity and regenerability in reactions of non-functionalized olefins but often have to be pretreated with an alkylating agent to increase the activity when functionalized olefins such as methyl oleate are used. Olefins having protic functional groups (such as hydroxyl groups, carboxyl groups or amino groups) lead to spontaneous deactivation of the heterogeneous catalyst.
In recent years, increasing efforts have been made to prepare homogeneous catalysts which are stable in a protic medium and in the presence of atmospheric oxygen. Catalysts which have been found to be of particular interest are specific ruthenium-alkylidene compounds. Such complexes and processes of preparing them are known.
WO 93/20111 describes ruthenium- and osmium-carbene complexes for olefin metathesis polymerization. The complexes have the structure RuX
2
(═CH—CH═CR
2
)L
2
. Ligands L used are triphenylphosphine and substituted triphenyl-phosphine. The preparation is carried out, for example, by reacting RuCl
2
(PPh
3
)
3
with suitable disubstituted cyclopropenes as carbene precursors. However, the synthesis of cyclopropene derivatives consists of a number of stages and is of little interest from an economic point of view.
Similar reactions are described in WO 96/04289. In addition, processes for olefin metathesis polymerization are indicated.
The use of such catalysts for peroxide-crosslinking of ROMP polymers is described in WO 97/03096.
WO 97/06185 likewise describes metathesis catalysts based on ruthenium-carbene complexes. Apart from the above-described process, they can also be prepared by reaction of RuCl
2
(PPh
3
)
3
with diazoalkanes. However, handling diazoalkanes poses a safety risk, particularly when the process is carried out on an industrial scale.
In addition, the organometallic starting materials of the formula RuCl
2
(PPh
3
)
3
have to be prepared from RuCl
3
.3H
2
O using a large excess of triphenylphosphine. Subsequently, PPh
3
ligands are again lost by ligand exchange in the catalyst synthesis itself. The carbene precursors used require multistage syntheses and do not have an unlimited shelf life.
Organometallics 1996, 15, 1960-1962 describes a process for preparing ruthenium complexes in which polymeric [RuCl
2
(cyclooctadiene)]
x
in i-propanol is reacted with hydrogen in the presence of phosphine. This eliminates the necessity of phosphine exchange. An undefined mixture of products is obtained. In addition, long reaction times are required when starting from a polymeric starting material. The cyclooctadiene present in the organometallic starting material does not contribute to the reaction and is lost.
J. Chem. Soc. Commun. 1997, 1733-1734 describes the synthesis of a methylene complex RuCl
2
(═CH
2
)(PCy
3
)
2
starting from dichloromethane and the ruthenium polyhydride RuH
2
(CH
2
)
2
(PCy
3
)
2
. However, the ruthenium-polyhydride complex is difficult to obtain. Furthermore, long reaction times are required.
The known synthetic routes for preparing metathesis catalysts of the type RuX
2
(═CH—CH
2
R)(PR′
3
)
2
are uneconomical for the reasons mentioned.
It is an object of the present invention to provide processes for preparing ruthenium alkylidene complexes of the type RuX
2
(═CH—CH
2
R)L
1
L
2
or RuXY(═CH—CH
2
R)L
1
L
2
, which processes lead, in a rapid and atom-economical reaction starting from readily available starting materials, to the desired products without ligand exchange. The processes should also be inexpensive and give high yields under mild reaction conditions.
We have found that this object is achieved by a process for preparing ruthenium complexes of the formula I
RuX
2
(═CH—CH
2
R)L
1
L
2
  (I)
where
X is an anionic ligand,
R is hydrogen or a substituted or unsubstituted C
1
-C
20
-alkyl radical or C
6
-C
20
-aryl radical and
L
1
and L
2
are, independently of one another, uncharged electron donor ligands, by
(a) reaction of RuX
3
with L
1
and L
2
in an inert solvent in the presence of a reducing agent and hydrogen and, without isolation of intermediates,
(b) subsequent reaction with compounds of the formula II
R—C≡CH  (II)
where R is as defined above, in the presence or absence of water.
This object is also achieved by a process for preparing ruthenium complexes of the formula IV
RuXY(═CH—CH
2
R)L
1
L
2
  (IV)
where
X, Y are identical or different anionic ligands,
R is hydrogen or a substituted or unsubstituted C
1
-C
20
-alkyl radical or C
6
-C
20
-aryl radical and
L
1
and L
2
are, independently of one another, uncharged electron donor ligands, by
(a) reaction of RuX
3
with L
1
and L
2
in an inert solvent in the presence of a reducing agent and hydrogen with compounds of the formula II
R—C≡CH  (II)
where R is as defined above, in the presence or absence of water, to form a compound of the formula V
RuXH(═C═CHR)L
1
L
2
  (V)
where X, R, L
1
, L
2
are as defined above,
(b) separation of the compound of the formula V from the reaction mixture and subsequent reaction with HY, (HL
1
)Y or (HL
2
)Y in an inert solvent with compounds of the formula II
R—C≡CH  (II)
where R is as defined above, in the presence or absence of water, and
(c) subsequent reaction with HY, [HL
1
]Y or [HL
2
]Y.
It has been found that the above mentioned ruthenium complexes can be obtained in very good yields directly from RuX
3
, preferably RuCl
3
.3(H
2
O), by simple reaction with ligands L
1
and L
2
, hydrogen and terminal alkynes of the formula II in the presence of reducing agents without isolation of intermediates. The ruthenium complexes have no vinylic substituents on the carbene carbon atom. The starting materials can be prepared inexpensively and are readily available.
To prepare the mixed-anion complexes of the formula IV, the intermediate of the formula V is isolated and subsequently reacted further. This enables different ligands X and Y to be introduced.
Firstly, the reaction of RuX
3
with the ligands L
1
and L
2
is carried out in an inert solvent in the presence of a reducing agent and hydrogen. Solvents which can be used are aromatics, heteroaromatics, cyclic or acyclic ethers. Preferred solvents are toluene, NMP, tetrahydrofuran, dialkyl ethers, glycol ethers and dioxane. Particular preference is given to tetrahydrofliran.
The reducing agent used can be any reducing agent which reduces Ru(III) to Ru(II) under the reaction conditions. The reduction is preferably carried out using hydrogen in the presence of a metallic or no

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