Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Organic compound containing
Reexamination Certificate
1999-10-07
2001-05-15
Vollano, Jean F. (Department: 1621)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Organic compound containing
C556S136000, C560S207000
Reexamination Certificate
active
06232262
ABSTRACT:
The invention relates to a novel catalyst system comprising a palladium compound, an acid compound having a pKa>2 measured in water of 18° C. and an non-symmetrical bidentate phosphorous ligand according to:
in which the —PR
1
R
2
group is different from the —PR
3
R
4
group, R
1
-R
4
are organic groups and X is a divalent organic bridging group, in which the direct link between the two phosphorous atoms in the bridging group X consists of a chain of
2
-10 carbon atoms and optionally a sulphur or oxygen atom.
In EP-A-273489 catalyst systems are described comprising palladium, a sterically hindered benzoic acid and a bidentate phosphine, i.e. 1,4-bis(diphenylphosphino) butane for use as catalyst in the carbonylation reaction of conjugated dienes and an alcohol to alkyl pentenoate compounds.
A disadvantage of this known catalyst composition is that the rate of reaction is relatively low when used as carbonylation catalyst. A need exists for a catalyst system which can increase the rate of this reaction (at a given temperature). Higher reaction rates also make it possible to operate at lower temperatures. This is advantageous because at lower temperatures less degradation of the catalyst system takes place. We have found that by using the catalyst system according to the invention the rate of the reaction can be improved considerably.
A catalyst system comprising palladium, an acid and non-symmetrical bidentate phosphine ligands, 1-(diisopropylphosphino)-1′-(phenylisopropylphosphino)-ferrocene is described in WO-A-9506027. This publication does not teach in any way that by using this non-symmetrical phosphine ligand higher reaction rates were to be expected. Moreover, only symmetrical phosphines were used in the examples. Furthermore it has been found that the disclosed catalyst system is less stable than the catalyst system according to the invention when used in a carbonylation reaction.
The non-symmetrical phosphine can be prepared by well known methods as for example described in GB-A-2101601.
Without being limited to the following theory it is believed that the improved reaction rate results from the fact that the electronic properties of the two phosphorous atoms of the ligand are different as a result of the different groups bonded to the phosphorous atoms. A larger difference in electronic properties of the two phosphorous atoms would result in a higher rate of reaction. Therefore it is preferred that one phosphorous atom is substituted with one or two electron withdrawing groups (R
1
, R
2
) while the other phosphorous atom is substituted with one or two electron donating groups (R
3
, R
4
). For example R
1
, R
2
and R
3
can be electron withdrawing groups while R
4
is an electron donating group. This effect can also be achieved when for example R
1
and R
2
are one divalent organic group while R
3
and R
4
are both monovalent organic groups. More preferably one phosphorous atom is substituted with only electron withdrawing groups while the other phosphorous atom is only substituted with electron donating groups. Examples of electron withdrawing groups are aryl groups optionally substituted with —F, —Cl, —Br, —I, —CF
3
, —SO
3
H, —NR
3+
, —NO
2
, —ONO
2
, —CO
2
H, —CO
2
R, —C(O)R, —NO and —ONO groups (R=C
1
-C
28
alkyl group),or —O—R
5
groups, in which R
5
is preferably an aryl group optionally substituted with the above described groups. Examples of electron donating groups are optionally substituted alkyl groups. Substituents of the alkyl groups is for example a —OR
6
-group, in which R
6
is an C
1
-C
28
alkyl group. Divalent cyclic alkylene groups are also examples of electron donating groups, provided that the number of C-atoms in the ring is equal or higher than 4.
Preferably optionally substituted C
1
-C
10
alkyl groups are used as electron donating groups and optionally substituted C
6
-C
10
aryl groups are used as electron withdrawing groups. Examples are methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, isobutyl, tert-butyl, cyclobutyl, pentyl, neopentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, cycloheptyl, octyl, cyclooctyl, nonyl, decyl, 2-cyanoethyl, 2-hydroxyethyl, 2-dialkylaminoethyl, 2-bromomethyl, vinyl, allyl, crotyl, phenyl, o-tolyl, p-tolyl, 1-methoxyphenyl, 2-methoxyphenyl, 3-methoxyphenyl, 1-fluorophenyl, 2-fluorophenyl, 3-fluorophenyl, pentafluorphenyl, 2,3-dimethylphenyl, 2,4-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 3,5-dimethylphenyl, 2,4,6-trimethylphenyl, 1-cyanophenyl, 2-cyanophenyl, 3-cyanophenyl, 1-&agr;, &agr;, &agr;-trifluorotolyl, 2-&agr;, &agr;, &agr;-trifluorotolyl, 3-&agr;, &agr;, &agr;-trifluorotolyl, naphthyl and benzyl. These alkyl groups and aryl groups are optionally (further) substituted with for example methyl, methoxy, cyanide or trifluoromethyl groups.
The bridging group X can be an organic group having between 2 and 20 carbon atoms with the proviso that the shortest direct link between the phosphorous atoms consists of 2 and 10 atoms. Preferably the direct link between the two phosphorous atoms in the bridging group X consists of a chain of 3-4 carbon atoms and optionally an additional non-terminal sulphur or oxygen atom.
Examples of possible non-symmetrical bidentate phosphine ligands are: 1-(diisopropylphosphino)-4-(diphenylphosphino)butane, 1-(dibutylphosphino)-4-(diphenylphosphino)butane, 1-(dicyclohexylphosphino)-4-(diphenylphosphino)butane, 1-(ditert-butylphosphino)-4-(diphenylphosphino)butane, 1-(tert-butylphenylphosphino)-4-(diphenylphosphino)butane, 1-(butylphenylphosphino)-4-(diphenylphosphino)butane, 1-(4,8-dimethyl-2-phosphabicyclo[3.3.1]nonane)-4-(diphenylphosphino)butane, 1-(9-bicyclo-phosphanonanyl)-4-(diphenylphosphino)butane, 1-(diisopropylphosphino)-3-(diphenylphosphino)propane, 1-(ditert-butylphosphino)-3-(diphenylphosphino)-propane or, 1-(cyclohexylphenylphosphino)-3- (diphenyl-phosphino)-propane.
The palladium can be present in the catalyst system in the form of a heterogeneous palladium compound or as a homogeneous palladium compound. Homogeneous systems are preferred. Since palladium forms complexes with the phosphine ligand, the choice of the initial Pd compound is in general not critical. Homogeneous palladium compounds include, for instance, palladium salts of, for instance, nitric acid, sulphonic acid, alkane carboxylic acids with not more than 12 carbon atoms or hydrogen halogenides (Cl, Br, I). Exemplary homogeneous palladium compounds include PdCl
2
, PdBr
2
, PdI
2
, Na
2
PdI
4
, K
2
PdI
4
, PdCl
2
(benzonitrile)
2
and bis(allylpalladium chloride). Another group of suitable halogen-free palladium compounds are palladium complexes such as palladium acetylacetonate (Pd(acac)
2
), Pd(II)acetate, palladiumnitrate Pd(NO
3
)
2
, tris(tri-o-tolyl phosphine) palladium, and di-palladium-tris-(dibenzylideneacetone) (Pd
2
(dba)
3
). An exemplary of a heterogeneous palladium compound is a palladium compound on an ion exchanger such as, for example an ion exchanger containing carboxylic acid groups. Ion exchangers containing carboxylic acid groups are commercially available under the brand names Amberlite IRC 50® and Amberlite IRC 84® (Rohm & Haas). Another heterogeneous catalyst is an immobilized phosphine on carrier catalyst, in which the palladium forms complexes with the immobilized phosphine (phosphine being the ligand of the catalyst system). Carriers include polystyrene, polyacrylamide, silica, alumina, silica-alumina or zeolite support.
The acid compound with a pKa>2 is generally a protonic acid, preferably having a pKa between 2-6 measured in water at 18° C. Preferred acids are carboxylic acids having 1 to 30 carbon atoms. These carboxylic acids may be substituted with hydroxy, C
1
-C
4
alkoxy groups, for example methoxy, amine or halogenide groups, for example Cl, I and Br. Exemplary carboxylic acids are benzoic acid, acetic acid, valeric acid, pentenoic acid, nonanoic acid and butanoic acid. The acid is preferably a sterically hindered carboxylic acid having a pKa of less than 4.5. Exemplary sterically hindered carboxylic aci
Agterberg Frank P. W.
Buijsen Paulus F. A.
Oevering Henk
Sielcken Otto E.
Toth Imre
DSM N?V?
Pillsbury & Winthrop LLP
Vollano Jean F.
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