Cationic ruthenium complexes, their production and their use

Details Cationic ruthenium complexes, their production and their use Cationic ruthenium complexes, their production and their use

2000-11-02

2002-12-31

Nazario-Gonzalez, Porfirio (Department: 1621)

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

Organic compounds

Heavy metal containing

C556S007000, C556S008000, C556S023000, C556S030000, C556S136000, C556S137000, C502S154000, C502S155000

Reexamination Certificate

active

06500975

ABSTRACT:

The present invention relates to cationic ruthenium complexes which can be used, for example, as catalysts in metathesis reaction and processes for their preparation.
Olefin metathesis (disproportionation) involves, in its simplest form, a reversible, metal-catalyzed transalkylidenation of olefins by rupture and reformation of carbon-carbon double bonds. In the case of the metathesis of acyclic olefins, a distinction is made, for example, between self-metathesis in which an olefin is transformed into a mixture of two olefins having different molar masses (for example conversion of propene into ethene and 2-butene) and cross-metathesis or cometathesis in which two different olefins react (for example propene with 1-butene to give ethene and 2-pentene). Further application areas of olefin metathesis include 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 concern the selective ring opening of cyclic olefins by means of acyclic olefins, and also ring closure reactions (RCM) by means of which, preferably starting from &agr;,&ohgr;-dienes, unsaturated rings of various ring sizes can be prepared.
Suitable catalysts for metathesis reactions are in principle homogeneous and heterogeneous transition metal compounds.
Heterogeneous catalysts, for example molybdenum, tungsten or rhenium oxides on inorganic oxidic supports, have 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 using finctionalized olefins such as methyl oleate. 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, increased efforts have been made to prepare homogeneous catalysts which are stable in protic medium and in the presence of atmospheric oxygen. Here, specific ruthenium alkylidene compounds have attracted particular interest. Such complexes and processes for their preparation 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 triphenylphosphine. The complexes are prepared, for example, by reacting RuCl
2
(PPh
3
)
3
with suitable disubstituted cyclopropenes as carbene precursors. However, the synthesis of cyclopropene derivatives involves a number of steps and is of little interest from a commercial point of view.
Similar reactions are described in WO 96/04289. Processes for olefin metathesis polymerization are also mentioned.
Use of such catalysts for peroxide crosslinking of ROMP polymers is described in WO 97/03096.
WO 97/06185 likewise describes metathesis catalysts which are based on ruthenium carbene complexes. Apart from the above-described method, they can also be prepared by reacting RuCI
2
(PPh
3
)
3
with diazoalkanes. However, handling diazoalkanes constitutes a safety risk, particularly when the process is carried out on an industrial scale.
In addition, the 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. In the catalyst synthesis itself, PPh
3
ligands are again lost as a result of ligand replacement. The carbene precursors used require multistage syntheses and do not keep indefinitely.
Organometallics 1996, 15, 1960 to 1962, describes a process for preparing ruthenium complexes in which polymeric [RuCI
2
(cyclooctadiene)]
x
is reacted with hydrogen in i-propanol in the presence of phosphine. This eliminates the need for the phosphine replacement. An undefined mixture of products is obtained. In addition, long reaction times are necessary when starting from a polymeric starting material. The cyclooctadiene present in the starting material does not contribute to the reaction and is lost.
J. Chem. Soc. Commun. 1997, 1733 to 1734, describes a synthesis of the methylene complex RuCI
2
(═CH
2
)(PCy
3
)
2
, which starts from dichloromethane and the ruthenium polyhydride complex RuH
2
(H
2
)
2
(PCy
3
)
2
. However, the ruthenium polyhydride complex is difficult to obtain. In addition, long reaction times are necessary.
The above ruthenium(II) alkylidene complexes, like all other known metathesis catalysts containing electron-rich transition metals, are unsuitable, or have only limited suitability, as catalysts for metathesis reactions of electron-poor olefins such as acrylic acid or derivatives thereof.
Catalyst systems based on molybdenum and tungsten have only very limited suitability for metathesis reactions of functionalized olefins. The most active catalysts involving electron-poor transition metals, e.g. the systems of the type (RO)
2
M(NR)(═CHR′)(M═Mo, W) described in EP-A-0 218 138, suffer not only from the disadvantage of a low activity in respect of such substrates but also the disadvantage of an extremely high sensitivity to impurities in the feed and are also of no interest from an economic point of view because of their very high preparation costs. In J. Am. Chem. Soc. 1995, 117, 5162 to 5163, Crowe describes the use of these catalysts for mechanistic studies on cross-metathesis reactions of acrylonitrile (H
2
C═CHCN) with H
2
C═CHR (R═electron-donating radical) to give NCHC═CHR and H
2
C═CH
2
, which proceed to only moderate conversions even at high catalyst concentration. U.S. Pat. No. 5,621,047 describes the ring-opening cross-metathesis of cyclooctadiene with methyl methacrylate using WCl
6
/SnMe
4
to give oligomers having carboxylic end groups.
Inexpensive catalyst systems which are stable to impurities in the feed and to atmospheric oxygen and are suitable for metathesis reactions in which electron-poor olefins participate are unknown hitherto.
It is an object of the present invention to develop a catalyst system for metathesis reactions of electron-poor olefins to enable metathesis reactions to be carried out on large-volume, basic industrial products such as acrylic acid and derivatives thereof, acrylonitrile, vinyl chloride, vinyl sulfone, etc. Apart from a high activity, a high stability to impurities in the feed and to atmospheric oxygen as well as a long operating life and inexpensive and uncomplicated synthesis from readily available raw materials should be realized.
We have found that this object is achieved by catalyst systems comprising as active components cationic ruthenium complexes of the formula
A
(cationic carbyne complexes) or
B
(cationic carbene complexes) or mixtures in which these are present,
where
B
may be stabilized by a further ligand L
4
. In the structures
A
and
B
, —C
X
−
is an anion which does not coordinate or coordinates only weakly to the metal center, for example a complex anion from main groups III to VII of the Periodic Table of the Elements, e.g. BR″
4
−
(R″=F or phenyl which may be substituted by one or more fluorine atoms or by polyfluorinated or perfluorinated C
1
-C
6
-alkyl radicals, for example C
6
H
5−n
F
n
where n=1 to 5), PF
6
−
, AsF
6
−
, SbF
6
−
, ClO
4
−
, CF
3
SO
3
−
or FSO
3
−
,
Y is a monodentate or multidentate anionic ligand,
R and R′ are each, independently of one another, hydrogen or a substituted or unsubstituted C
1
-C
20
-alkyl, C
6
-C
20
-aryl or C
7
-C
20
-alkylaryl or aralkyl radical,
L
1
, L
2
, L
3
and L
4
are, independently of one another, uncharged electron donor ligands, preferably nitrogen donors, for example amines and pyridines, phosphines, arsines, stibines, bearing at least two bulky radicals such as i-propyl, t-butyl, cyclopentyl, cyclohexyl, methyl or the like, or else &pgr;-coordinated olefins or solvent molecules.
The groups preferably have the following meanings:
X
−
is BR″
4
−
wher

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