GB2370516A - Catalyst composition for the preparation of copolymers of carbon monoxide and an olefinically unsaturated compound - Google Patents

Abstract

A catalyst composition comprising <SL> <LI>a) a source of palladium cations, and <LI>b) a ligand of the general formula </SL> <BR> R<SP>1</SP>R<SP>2</SP>M<SP>1</SP>-R<SP>5</SP>-M<SP>2</SP>R<SP>3</SP>R<SP>4</SP> (1)<BR> <BR> wherein each of M<SP>1</SP> and M<SP>2</SP> independently represents phosphorous, nitrogen, arsenic or antimony,<BR> wherein each of R<SP>1</SP> to R<SP>4</SP> independently represents an optionally substituted hydrocarbyl group, wherein R<SP>5</SP> represents a bivalent bridging group of which the bridge, which extends directly between the atoms M<SP>1</SP> and M<SP>2</SP>, consists of two bridge atoms which are linked to one another by a saturated bond and at least one of which carries at least one substituent, and wherein if both bridge atoms carry a substituent and said substituents are linked to one another such that the substituents together with the interjacent bridge atoms form a ring, the ring is a four or five membered ring, provided that the ligand is not trans-2,3-bis(diphenylphosphino)-bicyclo[2.2.1]heptene-5. A process for the preparation of copolymers of carbon monoxide and at least one olefinically unsaturated compound is also disclosed.

Description

CATALYST COMPOSITION AND PROCESS FOR THE PREPARATION OF COPOLYMERS OF CARBON MONOXIDE AND AN OLEFINICALLY UNSATURATED COMPOUND

The invention relates to a catalyst composition and a process for the preparation of copolymers of carbon monoxide and at least one olefinically unsaturated compound.

Linear copolymers of carbon monoxide with one or more olefinically unsaturated compounds can be prepared by contacting the monomers in the presence of a Group VIII metal containing catalyst (Groups 8,9 and 10 in modern notation as given in the Periodic Table as published in the CRC Handbook of Chemistry and Physics, 68th Edition, 1985, CRC Press, Inc. ). The copolymers can be processed by means of conventional techniques into films, sheets, plates, fibres and shaped articles for domestic use and for parts in the car industry. They are eminently suitable for use in many outlets for thermoplastics. In the copolymers in question the units originating from the carbon monoxide on the one hand and the units originating from the at least one olefinically unsaturated compound on the other hand may occur in an alternating or substantially alternating arrangement.

To date, polymers of carbon monoxide with one or more olefinically unsaturated compounds have generally been prepared using prior art catalyst compositions based upon: a) source of palladium cations, b) compound of the general formula RlR2Ml-Q-M2R3R4, wherein Ml and M2 represent similar or different elements chosen from the group made up of arsenic, antimony, phosphorus and nitrogen, wherein R, R2, R3 and R4

represent similar or different hydrocarbyl groups which may optionally be substituted with polar groups and wherein Q is a bivalent bridging group of at least 1 atom.

In the afore-mentioned class of polymer preparation, the rate of polymerisation is important with regard to the cost effectiveness and the efficiency of the process.

Polymerisation rates may be increased by raising reaction temperature, however this can have a detrimental effect on the quality of the copolymer prepared. For example, at otherwise similar reaction conditions an increase in reaction temperature will generally lead to an increase in reaction rate but also to a decrease in the molecular weights of the polymers obtained. The latter is disadvantageous as polymers are frequently more valuable with a view to their uses as they have higher molecular weights. Increasing reaction temperature may also increase processing costs.

With regard to polymerisation rates, the activity of catalyst compositions comprising a ligand of general formula RlR2Ml-Q-M2R3R4, wherein Q represents a 1,3-propylene bridging group, are substantially higher than that of catalysts comprising a similar ligand wherein Q represents a 1,2-ethylene bridging group. For example, by comparing run 19 with run 18 of EP-A-121965 it can be seen that under otherwise unchanged conditions a much greater rate of polymerisation is achieved using a catalyst containing a ligand of formula Ph2P-CH2-CH2 CH2-PPh2 than with a catalyst containing a ligand of formula Ph2P-CH2-CH2-PPh2.

The enhanced activity of catalysts based on ligands having 1,3-propylene bridging groups compared to catalysts based on ligands having 1,2-ethylene bridging groups is well documented, with several hypotheses having been proposed to account for the effect.

Drent and co-workers reporting in the Journal of Organometallic Chemistry, (1991, Vol. 417 pp 235-251, see page 246) suggested that in the catalysis mechanism, the square-planar palladium (II) ground state will alternate with a trigonal-bipyramidal transition state. The energy barrier between the two states is greater in catalysts based on ligands having 1, 2-ethylene bridging groups than in those based on ligands having 1, 3-propylene bridging groups and this lowers their activity. Chein and coworkers reporting in Macromolecular Chemistry, (1993, Vol. 194, pp 2579-2603, see pages 2593-2594), proposed an alternative theory wherein catalyst activity is related to the ability of a bisphoshine chelate to ring open. The chelates of catalysts based on ligands having 1,3propylene bridging groups ring open more readily than those based on ligands having 1, 2-ethylene bridging groups, and this increases their catalytic activity. A further rationale has been put forward by Baron et al. in Organometallics (1996, Vol. 15, pp 2213-2226, see pages 2216-2218) wherein the formation of a more stable metallacycle involving intra-molecular interaction between the b carbonyl group of the propagating polymer and the palladium centre is said to reduce the activity of catalysts based on ligands having 1, 2-ethylene bridging groups.

Whilst discussion continues as to the exact reasons for the reactivity difference, it is well known by those skilled in the art that in the preparation of copolymers of carbon monoxide and unsaturated compounds, reaction rates achieved using catalysts based on ligands having 1,3-propylene bridging groups are superior to those achieved using catalysts based on ligands having 1,2-ethylene bridging groups. Therefore, someone skilled in the art looking to obtain a good rate of polymerisation would be led to conclude that a catalyst based

on a ligand having a 1, 3-propylene bridging group must be used.

EP-A-384517 describes copolymers of carbon monoxide with an alpha-olefin having at least 3 carbon atoms in the molecule, having alternating CO-and alpha-olefinderived units and a stereo-regular structure, and their preparation by a process using a catalyst composition based upon (a) a palladium compound, (b) an anion of an acid with a pKa of less than 2 and (c) an asymmetric bisphosphine of the general formula R3R4P-R5-PR3R4, wherein R3 and R4 are identical or different optionally

polar-substituted hydrocarbon groups and R5 is a bridging group containing at least 2 carbon atoms in the bridge that connects the 2 phosphorous atoms. At column 4 lines 47 to 53, it is mentioned that nan example of an asymmetric bisphosphine in which the bridge that connects the two phosphorous atoms with one another contains two carbon atoms which together form part of a cyclic structure is trans-2, 3-bis (diphenylphosphino) bicyclo [2. 2. 1] heptene-5". The specific examples of the process of EP-A-384517 contain no example employing this asymmetric bisphosphine, or any other asymmetric bisphosphine in which the bridge that connects the two phosphorus atoms with one another contains two carbon atoms which together form part of a cyclic structure.

Indeed, in all of the specific examples of the process of EP-A-384517, the asymmetric biphosphines all contain 1,4-butylene bridging groups (Examples 3 to 5). The comparative examples (1 and 2) make use of symmetrical bisphosphines containing a 1,3-propylene bridge.

Further research into this class of catalyst has now surprisingly shown that the performance of catalyst compositions based on ligands having two bridge atoms linked to one another by a saturated double bond may be substantially improved by the incorporation of at least

one substituent onto at least one bridge atom, and wherein if both bridge atoms carry a substituent and said substituents are linked to one another such that the substituents together with the interjacent bridge atoms form a ring, the ring is a four or five membered ring.

Accordingly the present invention provides a catalyst composition which is based on, a) a source of palladium cations, and b) a ligand of the general formula RlR2Ml-R5-M2R3R4 (1) wherein each of Ml and M2 independently represents phosphorous, nitrogen, arsenic or antimony, wherein each of Rl to R4 independently represents an optionally substituted hydrocarbyl group, wherein R5 represents a bivalent bridging group of which the bridge,

which extends directly between the atoms MI and M2, consists of two bridge atoms which are linked to one another by a saturated bond and at least one of which carries at least one substituent, and wherein if both bridge atoms carry a substituent and said substituents are linked to one another such that the substituents together with the interjacent bridge atoms form a ring, the ring is a four or five membered ring, provided that the ligand is not trans-2,3-bis (diphenylphosphino) -

bicyclo [2. 2. 1] heptene-5.

The catalyst compositions of the present invention require a source of palladium cations. Suitable sources of palladium cations include palladium salts of mineral acids, such as salts of sulphuric acid, nitric acid and phosphoric acid, and salts of sulphonic acids, such as methanesulphonic acid and para-toluenesulphonic acid.

Preferred sources are salts of carboxylic acids, in particular those having up to 6 carbon atoms, such as acetic acid, propionic acid and trifluoroacetic acid. The source of palladium cations may be a palladium halide,

for example palladium chloride or palladium bromide. If desired, as cation source use may be made of palladium in its elemental form, or in a zero-valent state thereof, e. g. in complex form, such as complexes wherein the palladium is covalently bonded to one or two hydrocarbyl groups.

A preferred source of palladium is palladium (II) acetate.

The catalyst compositions of the present invention are based on a ligand of the general formula RlR2Ml-R5-M2R3R4 (1) wherein Ml and M2 represent independently phosphorous, nitrogen, arsenic or antimony. Preferably M1 and M2 both represent the same atom type. Most preferably M1 and M2 both represent phosphorous atoms.

In general formula (1), each of R1 to R4 independently represents an optionally substituted hydrocarbyl group. Preferred optionally substituted hydrocarbyl groups include optionally substituted alkyl, alkaryl, aryl, aralkyl or cycloalkyl groups.

Optional substituents in groups Rl to R4 include halogen atoms, such as fluorine and chlorine, haloalkyl and haloalkoxy groups having 1 to 6 carbon atoms, and groups of the general formula R'-O-, R'-S-, R'-CO-, R'

CO-O-, R'-CO-NH-, R'-CO-NR"-, R'R"N-, R'R"N-CO-, R'-O-CO NH-and R'-O-CO-NR", wherein R'and R"represent the same or different hydrocarbyl groups preferably containing up to 6 carbon atoms and wherein R"may also represent a hydrogen atom.

Preferred substituents in groups R1 to R4 are alkoxy groups, alkylamino groups and dialkylamino groups.

Preferably, the alkyl substituents in such alkoxy, alkylamino and dialkylamino groups contain up to 4 carbon atoms. Preferred alkoxy groups are methoxy and ethoxy

groups ; preferred alkylamino groups are methylamino and ethylamino groups, and preferred dialkylamino groups are dimethylamino and diethylamino groups.

Most preferred substituents in groups Rl to R4 are alkoxy groups, in particular, methoxy groups.

Particularly preferred optionally substituted hydrocarbyl groups Rl to R4 are optionally substituted aryl groups. Preferred optionally substituted aryl groups are optionally substituted phenyl groups. Particularly preferred such aryl groups are phenyl, 2-methoxy phenyl, 2,4-dimethoxyphenyl, and 4-methoxyphenyl groups.

It is preferred that at least one of Rl and R2 and at least one of R3 and R4 represents an optionally substituted aryl group. Preferably each of Rl to R4 independently represents an optionally substituted aryl group, more preferably an aryl group optionally substituted with at least one alkoxy group. Conveniently, for ease of preparation, each of Rl to R4 may independently represent an aryl group which does not bear a substituent, for example a phenyl group.

In bridging group R5, the bridge, which extends directly between the atoms MI and M2, consists of two bridge atoms at least one of which carries at least one substituent. The bridge atoms are preferably carbon atoms but it is also feasible that at least one of the bridge atoms is a silicon or nitrogen atom.

Conveniently, R5 may represent a bivalent bridging group of which the bridge, which extends directly between the atoms Ml and M2, is a 1,2-ethylene group of formula - CXlyl-CX2y2-, (2) wherein each of Xl and X2 independently represents a hydrogen atom or a substituent and wherein each of yl and y2 independently represents a substituent.

Substituents which a bridge atom may conveniently carry, e. g. any of XI, X2 y1 and y2 in formula (2), include monovalent substituents consisting of carbon, hydrogen and optionally phosphorous, oxygen, nitrogen and/or halogen atoms. Preferred such substituents of bridge atoms include optionally substituted alkyl, alkanoyl and alkoxy groups. Preferably, the alkyl substituents in such alkyl, alkanoyl and alkoxy groups contain up to 6, preferably up to 4, carbon atoms in their alkyl moiety, not including carbon atoms of substituents thereof. Optional substituents of such alkyl, alkanoyl, and alkoxy groups include cyano groups; alkoxy groups having 1-4 carbon atoms; and amino, mono (Cl-4-alkyl) amino and di (Cl-4-alkyl) amino groups; dialkylphosphino groups and diarylphosphino groups.

Further preferred such substituents of bridge atoms are optionally substituted aryl groups, particularly phenyl groups. Optional substituents of such aryl groups include nitro, hydroxyl and cyano groups; alkyl, alkoxy, haloalkyl and haloalkoxy groups having 1-4 carbon atoms; and amino, mono (Cl-4-alkyl) amino and di (Cl-4-alkyl) amino groups. Up to three optional substituents may suitably be employed.

Particularly preferred substituents of bridge atoms are monovalent substituents consisting of carbon, hydrogen and optionally phosphorous and/or oxygen atoms, for example alkyl groups optionally substituted with dialkylphosphino or diarylphosphino groups.

In formula (2), it is preferred that each of XI and X2 independently represents a hydrogen atom or an optionally substituted alkyl group. More preferably, each of Xl and X2 independently represents a hydrogen atom or an n-alkyl group and most preferably Xl and X2 both represent hydrogen atoms.

It is preferred that each of yl and y2 independently represents an optionally substituted hydrocarbyl group.

More preferably each of yl and y2 independently represents an unsubstituted alkyl group, most preferably an n-alkyl group. An alkyl group forming yl or y2 preferably has up to 6 carbon atoms, most preferably up to 4 carbon atoms. Most preferred alkyl groups are methyl and ethyl groups.

If both bridge atoms carry a substituent and said substituents are linked to one another such that the substituents together with the interjacent bridge atoms form a ring, the ring is a four or five membered ring, which ring is preferably a monocyclic ring system, i. e. said ring does not form part of a bicyclic or polycyclic ring system.

The substituents on the bridge atoms may conveniently be linked to one another by a chemical bond or by one or more interjacent atoms. Preferably they are linked to one another by a chemical bond.

Conveniently, y1 and y2 may be linked such that y1 and y2 together represent an optionally substituted bridging chain containing two or three chain atoms, preferably chain carbon atoms. The chain atoms may conveniently be unsubstituted such that the bridge atoms and the bridging chain together represent a cyclobutylene or cyclopentylene group, preferably a cyclobutylene group.

Advantageously, yl and y2 together may represent a bridging chain of formula

- CH (M3R5R6) (czlz2) n-CH (M4R7R8)- (3) wherein n is 0 or 1, wherein each of Zl and Z2 independently represents a hydrogen atom or a substituent, wherein each of M3 and M4 independently represents phosphorous, nitrogen, arsenic or antimony,

and wherein each of R5 to R8 independently represents an optionally substituted hydrocarbyl group. When n is 1, it is preferred that Zl and Z2 both independently represent a hydrogen atom or an n-alkyl group. Preferably Zl and Z2 both represent hydrogen atoms. More preferably n is 0.

Preferably M3 and M4 both represent the same atom type. Most preferably M3 and M4 both represent phosphorous atoms.

Optionally substituted hydrocarbyl groups which R5 to R8 represent are the same as those described earlier for groups Rl to R4, and groups and substituents which are preferred for RI to R4 are similarly preferred for R5 to R8. Preferably, at least one of R5 and R6 and at least one of R7 and R8 represents an optionally substituted aryl group. Most preferably each of R5 to R8 independently represents an optionally substituted aryl group.

When the catalyst compositions of the present invention are based on a ligand containing a bridging

chain of formula (3) it is preferred that each of Ml to M4 represent the same atom type. More preferably each of Ml to M4 represents a phosphorous atom. It is preferred that at least one of RI and R2, at least one of R3 and R4, at least one of R5 and R6 and at least one of R7 and

R8 represents an optionally substituted aryl group. Most preferably each of Rl to R8 independently represents an optionally substituted aryl group, more preferably an aryl group optionally substituted with at least one alkoxy group. Conveniently, for ease of preparation, each of Rl to R8 may independently represent an aryl group which does not bear a substituent, for example a phenyl group.

Accordingly, examples of a particularly preferred ligand of general formula (1), wherein at least one of the bridge atoms is substituted with at least one substituent are isomers and mixtures of isomers of 2,3-bis (diphenylphosphino) butane.

An example of a ligand of general formula (1) wherein both bridge atoms carry a substituent and said substituents are linked to one another such that the substituents together with the interjacent bridge atoms form a ring, which is a four or five membered ring, is cis, trans, cis-1, 2,3, 4-tetrakis (diphenylphosphino) cyclobutane.

The skilled person will recognise that the ligands of the present invention may contain one or more chiral centres. When this is the case, the ligand may be a single stereoisomer, or a mixture of any two or more stereoisomers.

For example, the ligand 2,3-bis (diphenylphosphino) butane contains two chiral centres. A molecule having two chiral centres may have a maximum of four stereoisomers (two pairs of enantiomers). In the case of 2,3-bis (diphenylphosphino) butane, two of the stereoisomers (one pair of enantiomers) are identical. This type of stereoisomer is termed a meso compound. Therefore 2,3-bis (diphenylphosphino) butane has only three stereoisomers, the meso compound and a pair of enantiomers. The meso compound is diastereomeric with the pair of enantiomers. A mixture containing two enantiomers in equal amounts is termed a racemic mixture or racemate.

For reasons of ease of synthesis, the ligand of the present invention may conveniently be a mixture of meso compound and racemate, meso compound alone, or racemate alone. A ligand very suitable for use in the catalyst compositions of the present invention is meso-2,3bis (diphenylphosphino) butane.

The amount of ligand applied may vary considerably, but is usually dependant on the amount of palladium present in the catalyst composition. The ligand of general formula (1) is preferably used in the catalyst compositions in a quantity of 0.1 to 2 and more preferably 0.5 to 1.5 mol per mol of palladium in the source of palladium cations. The preferred quantities of ligand described above are best suited to catalyst compositions wherein each ligand of general formula (1) co-ordinates with one palladium atom. The skilled person will recognise that in catalyst compositions where the ligand of general formula (1) co-ordinates with two or more palladium atoms, as in the case of cis, trans, cis1,2, 3,4-tetrakis (diphenylphoshino) cyclobutane, the preferred quantity of ligand will be proportionally less, e. g. a ligand which co-ordinates with two palladium atoms is preferably used in a quantity of 0.05 to 1 and more preferably 0.25 to 0.75 mol per mol of palladium in the source of palladium cations.

The catalyst compositions of the present invention are advantageously based on a source of anions as a further catalyst component. The skilled person will appreciate that suitable anions are those which are nonor only weakly co-ordinating with the palladium metal under the conditions of the copolymerisation. Examples of suitable anions are anions of protic acids, which include acids which are obtainable by combining a Lewis acid and a protic acid. Preferred acids are strong acids, i. e. those which have a pKa of less than 6, preferably less than 4, more preferably less than 2, when measured in aqueous solution at 18 oc. Examples of suitable protic acids are the above mentioned acids which may also participate in the palladium salts, e. g. trifluoroacetic acid and para-toluenesulfonic acid. Examples of Lewis acids which can be combined with a protic acid are as the

Lewis acids defined and exemplified hereinafter, in particular boron trifluoride, boron pentafluoride, tin dichloride, tin difluoride, tin di (methylsulphonate), aluminium trifluoride and arsenic pentafluoride, triphenylborane, tris (perfluorophenyl) borane and tris [3, 5-bis (trifluoro-methyl) phenyl] borane. Examples of protic acids which may be combined with a Lewis acid are sulphonic acids and hydrohalogenic acids, in particular hydrogen fluoride. Very suitable combinations of a Lewis acid with a protic acid are tetrafluoroboric acid and hexafluoroboric acid (HBF4 and HBF6). Other suitable anions are anions of which it appears that there are no stable conjugated acids, such as tetrahydrocarbylborate anions or carborate anions. Borate anions may comprise the same or different hydrocarbyl groups attached to boron, such as alkyl, alkaryl, aryl, aralkyl, and cycloalkyl groups. Preferred are tetraarylborates, such

as tetraphenylborate, tetrakis [3, 5-bis (trifluoromethyl)phenyl] borate and tetrakis (perfluorophenyl) borate, and carborate (BCH] ").

The source of anions may be an acid from which the anions are derivable, or their salts. Suitable salts are, for example, cobalt and nickel salts. Other sources of anions are suitable Lewis acids, such as halides, in particular fluorides, of boron, tin, antimony, aluminium or arsenic. Boron trifluoride and boron pentafluoride are very suitable. Other suitable Lewis acids are hydrocarbylboranes. The hydrocarbyl-boranes may comprise one hydrocarbyl group or two or three of the same or different hydrocarbyl groups attached to boron, such as alkyl, alkalyl, aryl, aralkyl, and cycloalkyl groups, preferably aryl groups. They may also comprise hydrocarbyloxy or hydroxy groups or halogen atoms attached to boron. Examples of very suitable hydrocarbylboranes are

triphenylborane, tris (perfluorophenyl) borane and tris [3, 5-bis (trifluoro-methyl) phenyl] borane.

Other suitable compounds which may function as a source of anions are those which are themselves acids or which are derivatives of acids, whereof the strength of said acids cannot be determined in aqueous solution at 18 C, since the acids are less stable in aqueous solution. Examples of such compounds are acids which are adducts of boric acid and a 1,2-diol, a catechol or a salicyclic acid.

Again other suitable compounds which may function as a source of anions are aluminoxanes, preferred aluminoxanes being methyl aluminoxanes and t-butyl aluminoxanes.

The skilled person will recognise that the quantity of the source of anions preferably used is dependant on the number of mol equivalents of anion that each mol of source of anions provides. Accordingly, the quantity of the source of anions is preferably selected such that it provides in the range of from 0.1 to 50 mol equivalents of anions per gram atom of palladium, more preferably in the range of from 0.5 to 25 mol equivalents of anions per gram atom of palladium metal. The aluminoxanes may be used in such a quantity that the molar ratio of aluminium to the palladium is in the range of from 4000: 1 to 10: 1, preferably from 2000: 1 to 100: 1, most preferably from 500: 1 to 200: 1.

The performance of the catalyst composition may be improved by incorporating therein an organic oxidant promoter, such as a quinone. Preferred promoters are selected from the group consisting of benzoquinone, naphthoquinone and anthraquinone. The amount of promoter is advantageously in the range of from 1 to 500, preferably in the range of from 2 to 100 mol per gram

atom of palladium metal in the source of palladium cations.

Copolymers of carbon monoxide and at least one olefinically unsaturated compound have been found to be readily prepared using catalyst compositions in accordance with this invention. Accordingly, a process in accordance with this invention comprises bringing, as monomers, carbon monoxide and at least one olefinically unsaturated compound into contact with one another in the presence of a catalyst composition in accordance with this invention.

Eligible examples of an at least one olefinically unsaturated organic compound that can be polymerised with carbon monoxide with the aid of the catalyst compositions according to the invention are compounds consisting of carbon and hydrogen and compounds which, in addition to carbon and hydrogen, contain one or more heteroatoms. The catalyst compositions according to the invention are preferably used for preparing polymers of carbon monoxide with at least one olefinically unsaturated hydrocarbon. Examples of preferred hydrocarbon monomers are ethene and other a-olefins such as propene, buten-1, hexen-1, octen-1 and decene-1, cyclic olefins such as cyclopentene, as well as styrene and alkyl-substituted styrenes such as para-methyl styrene and para-ethyl styrene or mixtures thereof. A particularly preferred hydrocarbon monomer is ethene.

The catalyst compositions according to the present invention may conveniently be used in the preparation of copolymers of carbon monoxide, ethene and optionally a further olefinically unsaturated compound.

Preferred further olefinically unsaturated compounds for copolymerisation with carbon monoxide and ethene are a-olefins having from 3 to 20 carbon atoms, for example propene, buten-1, octen-1 and decene-1.

In accordance with a further aspect of the present invention there is provided a process for the preparation of copolymers of, as monomers, carbon monoxide, ethene and optionally a further olefinically unsaturated compound comprising bringing the monomers into contact with one another in the presence of a catalyst composition which is based on a) a source of palladium cations, and b) a ligand of the general formula RIR2Ml-R5-M2R3R4 wherein each of M1 and M2 independently represents phosphorous, nitrogen, arsenic or antimony, wherein each of R1 to R4 independently represents an optionally substituted hydrocarbyl group, wherein R5 represents a bivalent bridging group of which the bridge,

which extends directly between the atoms M1 and M2, consists of two bridge atoms which are linked to one another by a saturated bond and at least one of which carries at least one substituent, and wherein if both bridge atoms carry a substituent and said substituents are linked to one another such that the substituents together with the interjacent bridge atoms form a ring, the ring is a four or five membered ring.

The inclusion of a further monomer into copolymers of carbon monoxide and ethene is advantageous as it results in a copolymer having a lower melting point.

A melting point as low as possible, whilst still retaining good properties in the products made from the copolymers, is desirable for ease of processing.

The quantity of catalyst composition used in the preparation of the copolymers may vary within wide ranges. Per mol of olefinically unsaturated compound to be polymerised, such a quantity of catalyst is preferably

used as to contain 10-7 to 10-3, and more preferably 10-6 to 10-4, gram atom of palladium.

The preparation of the polymers is preferably carried out at a temperature of 20-200 Oc and more preferably at a temperature of 30-150 C. The preparation of the polymers is preferably carried out at a pressure of 0.5 MPa to 20 MPa and more preferably at a pressure of 1 MPa to 10 MPa. In the mixture to be polymerised, the molar ratio of carbon monoxide relative to the at least one olefinically unsaturated organic compounds is preferably in the range of from 5: 1-1: 10 and most preferably 2: 1-1: 5.

The carbon monoxide used in the polymer preparation of the invention need not be pure. It may contain such contaminants as hydrogen, carbon dioxide and nitrogen.

The process of the invention is conveniently carried out in the presence of a diluent. Preferably a diluent is used in which the copolymers are insoluble or virtually insoluble so that they form a suspension upon their formation. Examples of types of diluent which may suitably be used in the process of the present invention includes aromatic solvents e. g. alkyl benzenes, halogenated alkanes e. g. dichloromethane, ketones e. g. acetone, ethers, esters and amides.

Very suitable diluents are hydroxylic liquids, e. g. monohydric and dihydric alcohols. Particularly preferred diluents are alcohols having at most 4 carbon atoms per molecule, such as methanol and ethanol. Preferably, the diluent is an organic hydroxylic liquid. Organic hydroxylic liquids may advantageously contain a minor quantity of water, for example 0.1-30 % wt, preferably 0.2-10 % wt, based on the total weight of the organic hydroxylic liquid. The process of this invention may also be carried out as a gas phase process, in which case the catalyst is typically used deposited on a solid

particulate material or chemically bound thereto. The process may also be carried out as an emulsion poly merisation reaction.

When a diluent is used in which the formed copolymer forms a suspension it is preferred to have a solid particulate material suspended in the diluent before the monomers are contacted with the catalyst composition.

Suitable solid particulate materials are silica, polyethene and a copolymer of carbon monoxide and an olefinically unsaturated compound, preferably a copolymer which is based on the same monomers as the copolymer to be prepared. The quantity of the solid particulate material is preferably in the range of from 0.1 to 20 g, particularly from 0.5 to 10 g per 100 g diluent.

The copolymers can be recovered from the polymerisation mixture by using conventional techniques.

When a diluent is used the copolymers may be recovered by filtration or by evaporation of the diluent. The copolymer may be purified to some extent by washing.

Copolymers may be suitably prepared in which the units originating from carbon monoxide on the one hand and the units originating from the at least one olefinically unsaturated compound on the other hand occur in an alternating or substantially alternating arrangement. The term"substantially alternating"will generally be understood by the skilled person as meaning that the molar ratio of the units originating from carbon monoxide to the units originating from the olefinically unsaturated compound (s) is above 35: 65, in particular above 40: 60. When the ratio is 50: 50, as is preferred, the copolymers are believed to be perfectly alternating.

The catalyst compositions of the present invention may be prepared by any convenient method. For example, they may be prepared by mixing a ligand of general formula (1) and a source of palladium cations. The resulting mixture, containing catalyst composition, may be used directly in copolymerisation reactions, or the catalyst composition may be isolated therefrom before being used in copolymerisation reactions.

Ligands of general formula (1) may be prepared by methods analogous to known methods, for example by reactions analogous to those described in EP-A-298540, e. g. see column 1 lines 26 to 49 and column 11, lines 28 to 44.

The present invention is illustrated by the following examples.

Catalyst complexes in accordance with the invention (1-3) and a comparative complex (A) were prepared as follows. In the preparations which follow, all reactions were carried out at ambient temperature (20 OC) and under an atmosphere of nitrogen, unless otherwise indicated.

Reagents and solvents were obtained from commercial suppliers. Petroleum ether had a boiling point in the range from 35-60 OC.

Catalyst Complex 1 Palladium meso-2,3-bis (diphenylphosphino) butane acetate

(Pd-meso- (CH3CH (PPh2)) 2 (OCOCH3) 2) Methanesulfonyl chloride (MsCl) (0. 233 mol) was added dropwise to a solution of meso-2,3-butanediol (0.111 mol) in dichloromethane (50 ml). The solution was allowed to stir overnight. The organic layer was washed with water (100 ml x 2), separated and pumped to dryness under reduced pressure. The crude solid obtained was recrystallized from a mixture of dichloromethane and

petroleum ether to give meso- (CH3CH (OMs)) 2 as a solid.

A solution of meso- (CH3CH (OMs)) 2 (23. 23 mmol) in tetrahydrofuran (THF) (60 ml) was added dropwise at 0 C to a solution of potassium diphenylphosphide dioxane adduct (55.00 mmol) in THF (100 ml). The mixture was

allowed to stir overnight. The solvent was then removed completely under vacuum and 100 ml of water was added to give a solid. The solid was filtered off, washed with petroleum ether and dried under vacuum overnight to yield meso- (CH3CHPPh2) 2.

Subsequently, a mixture of meso- (CH3CHPPh2) 2 (0.939 mmol) and Pd (II) chloride (0.939 mmol) in 20 ml of dimethylformamide (DMF) was stirred for 12 hours. During the reaction a solid precipitated. The suspension was concentrated to ca. 4 ml under reduced pressure. Then 30 ml of petroleum ether was slowly added to give more solid. The solid formed was filtered off, washed with petroleum ether and dried under nitrogen to yield Pd {meso- (CH3CHPPh2) 2} Cl2.

Finally, to a 20 ml dichloromethane solution of Pd {meso- (CH3CHPPh2) 2} Cl2 (0.464 mmol) was added silver acetate (1.16 mmol). After 5 hours stirring the mixture was passed through a column of filter material to remove silver chloride formed. The solution was concentrated under vacuum to ca. 2 ml. Addition of 30 ml of diethyl ether at 0 OC gave Catalyst complex 1 as a solid.

Catalyst Complex 2 Palladium racemic-2,3-bis (diphenylphosphino) butane acetate

(Pd-rac- (CH3CH (PPh2)) 2 (OCOCH3) 2) Racemic (rac)- (CH3CH (OMs)) 2 was obtained by fractional recrystallisation of an isomeric mixture of (CH3CH (OMs) ) 2 from a mixture of dichloromethane and ethanol, the rac (CH3CH (OMs) ) 2 separated first.

Next, rac- (CH3CH (OMs) ) 2 was converted into rac- (CH3CHPPh2) 2, then Pd {rac- (CH3CHPPh2) 2} C12 and finally Catalyst complex 2, in substantially the same manner as

meso- (CH3CH (OMs)) 2 was converted into Catalyst complex 1.

Catalyst Complex 3 Palladium cis, trans, cis-1, 2, 3, 4-tetrakis (diphenylphosphino) cyclobutane acetate (Pd2 (PPh2CH) 4 (OCOCH3) 4) Cis, trans, cis-1,2, 3,4-tetrakis (diphenylphosphino) cyclobutane was prepared by the procedure detailed in Inorganic Chimica Acta. 1999, Vol. 290, page 167, page 170-171.

To a 4 ml dichloromethane solution of Pd (II) acetate (0.135 mmol) was added cis, trans, cis-1, 2,3, 4-tetrakis (diphenylphosphino) cyclobutane (0.068 mmol). The solution was stirred for 15 hours. Upon slow addition of 30 ml of diethyl ether a solid was formed. The solid was filtered, washed with diethyl ether and dried under vacuum for 2 hours to yield Catalyst complex 3.

Catalyst Complex A (for comparison) Palladium 1,2-bis (diphenylphosphino) ethane acetate (Pd (CH2 (PPh2)) 2 (OCOCH3) 2) To a 10 ml methanol solution of Pd (II) acetate was added a dichloromethane solution of 1,2-bis (diphenylphosphino) ethane (0.753 mmol). The mixture was stirred for 20 minutes. The solution was then concentrated to ca. 1 ml under vacuum. Addition of 30 ml of petroleum ether gave a solid which was filtered off, washed with petroleum ether and dried under nitrogen to yield Catalyst complex A.

Examples 1-3, Comparative Example A Copolymers of carbon monoxide and ethene were prepared using catalyst complexes 1-3 (Examples 1-3) and comparative complex A (Comparative Example A), as follows.

A stirred 250 ml autoclave was charged, under nitrogen, with a catalyst solution consisting of 100 ml of methanol, 0.01 mmol of Catalyst complex, 0.2 mmol of para-toluenesulfonic acid, and 0.8 mmol of 1,4-benzoquinone.

The autoclave was then pressurised with 2 MPa of ethene and additionally with 2 MPa of carbon monoxide. After the contents of the autoclave had been brought to a temperature of 85 Oc the pressure was maintained by introducing under pressure a 1: 1 carbon monoxide/ethene mixture. After 3 hours the polymerisation was terminated by cooling the mixture to ambient temperature and subsequently releasing the pressure from the autoclave.

The copolymer was recovered by filtration, washed with methanol and allowed to dry.

Results are displayed in Table 1.

Table 1

Example 1 2 3 Comp. A Catalyst 1 2 3 A complex Copolymer 11. 1 8. 8 9. 8 1. 1 Productivity Kg/g Pd P-P ligand p p p (p P P mess rac

Examples 4-5, Comparative Example B Copolymers of carbon monoxide, ethene and propene were prepared using catalyst complexes 1-2 (Examples 4-5) and comparative complex A (Comparative Example B). An autoclave was charged with catalyst composition in substantially the same manner as described for Examples 1-3. The autoclave was then cooled to 4 OC and 20 g of propene introduced. The autoclave was subsequently pressurised with 2MPa of ethene and 2MPa of carbon monoxide and heated to a temperature of 85 OC.

After 3 hours the polymerisation was terminated and the copolymer recovered by filtration, washed with methanol and allowed to dry.

Results are displayed in Table 2.

Table 2

Example 5 6 Comp. B Catalyst complex 1 2 A Copolymer 6. 8 4. 5 1. 0 Productivity Kg/g Pd P-P ligand Cp P P meso rac The beneficial effects of using a catalyst composition comprising a ligand according to the invention in place of a corresponding unsubstituted ligand of formula R-R2p-CH2-CH2-PR3R4, are evident when comparing Examples 1 to 3 with comparative Example A; and when comparing Examples 4 and 5 with comparative Example B. It can be seen that under otherwise identical conditions, the use of catalyst complexes in accordance with the present invention leads to significantly improved polymerisation rates. For example, the catalyst composition of Example 1 is ten times more active than that of comparative Example A.

Claims (11)

C L A I M S

1. A catalyst composition which is based on, a) a source of palladium cations, and b) a ligand of the general formula RlR2Ml-R5-M2R3R4 wherein each of M1 and M2 independently represents phosphorous, nitrogen, arsenic or antimony,

wherein each of Rl to R4 independently represents an optionally substituted hydrocarbyl group, wherein R5 represents a bivalent bridging group of which the bridge, which extends directly between the atoms Ml and M2, consists of two bridge atoms which are linked to one another by a saturated bond and at least one of which carries at least one substituent, and wherein if both bridge atoms carry a substituent and said substituents are linked to one another such that the substituents together with the interjacent bridge atoms form a ring, the ring is a four or five membered ring, provided that the ligand is not trans-2,3-bis (diphenylphosphino) -

bicyclo [2. 2. 1] heptene-5.

2. A catalyst composition according to claim 1 characterised in that R5 represents a bivalent bridging group of which the bridge, which extends directly between the atoms M1 and M2, is a 1,2-ethylene group of formula - CX1Yl-CX2y2-, (2) wherein each of Xl and X2 independently represents a hydrogen atom or a substituent and wherein each of yl and y2 independently represents a substituent.

3. A catalyst composition according to claim 1 or claim 2, characterised in that Xl and X2 both represent a

hydrogen atom and each of y1 and y2 independently represents an n-alkyl group or y1 and y2 together represent a bridging chain of formula - CH (M3R5R6)- (CZlZ2) n-CH (M4R7R8) - (3) wherein n is 0 or 1,

wherein each of Zl and Z2 independently represents a hydrogen atom or a substituent, wherein each of M3 and M4 independently represents phosphorous, nitrogen, arsenic or antimony, and wherein each of R5 to R8 independently represents an optionally substituted hydrocarbyl group.

4. A catalyst composition as claimed in claim 3, characterised in that in formula (3) n is 0.

5. A catalyst composition as claimed in any one of claims 1 to 4, characterised in that each of M1 to M4 represents a phosphorous atom.

6. A catalyst composition according to any one of claims 1 to 5, characterised in that the ligand is a 2,3-bis (diphenylphosphino) butane or cis, trans, cis1,2, 3,4-tetrakis (diphenylphosphino) cyclobutane.

7. A catalyst composition according to any one of claims 1-6 further comprising a source of anions.

8. A catalyst composition according to claim 7 characterised in that the source of anions is an acid having a pKa of less than 6, when measured in aqueous solution at 18 oc.

9. A process for the preparation of copolymers of, as monomers, carbon monoxide and at least one olefinically unsaturated compound comprising bringing the monomers into contact with one another in the presence of a catalyst composition as claimed in any one of claims 1 to 8.

10. A process for the preparation of copolymers of, as monomers, carbon monoxide, ethene and optionally a further olefinically unsaturated compound comprising

bringing the monomers into contact with one another in the presence of a catalyst composition which is based on a) a source of palladium cations, and b) a ligand of the general formula RlR2Ml-R5-M2R3R4 wherein each of M1 and M2 independently represents phosphorous, nitrogen, arsenic or antimony, wherein each of R1 to R4 independently represents an optionally substituted hydrocarbyl group, wherein R5 represents a bivalent bridging group of which the bridge,

which extends directly between the atoms M1 and M2, consists of two bridge atoms which are linked to one another by a saturated bond and at least one of which carries at least one substituent, and wherein if both bridge atoms carry a substituent and said substituents are linked to one another such that the substituents together with the interjacent bridge atoms form a ring, the ring is a four or five membered ring.

11. A process according to claim 9 or claim 10, characterised in that the monomers are contacted with one another in an organic hydroxylic liquid diluent, using such an amount of the catalyst composition that the

amount of palladium present is in the range of from 10-7 to 10-3 gram atom per mole of the at least one olefinically unsaturated compound to be polymerised, and applying a temperature in the range of from 20 to 200 oc, and a pressure in the range of from 0. 5 MPa to 20 MPa.