Hydroformylation is a major industrial process that involves the reaction of carbon monoxide and hydrogen with an alkene to give an aldehyde. For most alkenes, two products are possible depending upon the regioselectivity of the addition reaction. The two products, linear (n) aldehyde and branched (i) aldehyde are generally obtained as a mixture but it is usually the linear product that is preferred for industrial applications.

There are currently two major industrial processes for the hydroformylation of alkenes. One process involves the use of cobalt catalysts, requires high temperatures and pressures and gives low n: i ratios. It is generally used for the production of higher aldehydes and alcohols (chain length > 5). The second major process involves the use of Rh/triphenylphosphine complexes. This process operates under mild conditions of temperature and pressure and provides high n: i ratios. It is generally used for hydroformylation of ethene and propene, but also for 2-propen-1-ol conversion to butanediol.

The two reactions referred to above are both carried out in the homogeneous phase (i. e. the catalyst, substrate and products are all dissolved in a common solvent) and this means that a process is required for the separation of products, solvent and catalyst.

Distillation is generally used, but the thermal sensitivity of the rhodium based catalysts means that they cannot be separated from longer chain aldehyde products (, C4). One way of circumventing this problem is to use a two phase system with the catalyst dissolved in water. Since the substrate and products are immiscible in water, separation can be effected in a simple manner. However, substrates with chain lengths of greater than 6 have such low solubility in water that the rate of the hydroformylation is too low for the aqueous process to be of commercial interest; and yet, it is just these substrates (C9-C14 aldehydes) that are of interest for the production of soaps and detergents. Consequently the Cg-Cl4 aldehydes are currently manufactured using the older, less selective, more energy intensive cobalt based systems.

There is thus a requirement for a more selective, less

energy intensive process for the formation of aldehydes which is also suitable for higher aldehydes.

Recently, a new approach to the problem of separating rhodium-based catalysts from reaction product has been suggested. This approach suggests the use a two phase system in which one of the phases is fluorinated and the other phase is organic. These phases are immiscible at room temperature but, by careful choice of the two solvents, can be made miscible at the reaction temperature. If the catalyst is designed to be soluble only in the fluorous phase, the reaction can be carried out in the monophasic higher temperature regime. Cooling effects phase separation such that the catalysts remain in the fluorous phase and the products are in the organic phase. Separation of the two phases can then be carried out and the fluorous phase containing the catalyst recycled.

Desirable properties of such a system are that the reaction rate should be high (comparable to that with Rh/PPh3), that the rhodium content of the organic phase at the end of the reaction should be negligible and that the n: i ratio should be high, preferably using only a small amount of phosphine relative to rhodium.

Horváth et al. describe the use of P (CH2CH2C6F13) 3 and [Rh (CO) 2 (acetylacetonate)] as catalyst precursors (see J. Am. Chem. Soc. 120: pages 3133-3143,1998). Good reaction rates and low solubilities of the rhodium complex in the organic phase were obtained but, even with a P: Rh ratio as high as 102: 1, the maximum n: i ratio was merely 7.84. An advantage of the system of the invention described below is that high rates and selectivity can be obtained using much less phosphorous compound.

EP-A-0,633,062 describes the use of [Rh (CO2) (acetylacetonate) with either P CH2CH2 (CF2) 5CF3 3 or P OCH2CH2 (CF2) 7CF3 3 at a P: Rh ratio of 40: 1.

The invention concerns new ligands for use in the fluorous biphasic hydroformylation of alkenes, which ligands allow the reaction to occur at rates similar to those obtained using Rh/PPh3 in organic solvents, which show little leaching of rhodium into the organic phase and which can provide high n: i ratios at low P: Rh loading. The ligands described herein also promote isomerisation of alkenes and can be used for the hydroformylation of internal alkenes giving significant amounts of n-aldehydes.

We have found that ligands of general formula I when complexed to a rhodium centre are especially good at catalysis of alkene hydroformylation in a fluorous multiphase system of the type described above.

Thus, the present invention provides a catalytic complex comprising a ligand of general formula I: (where X is O, S, C=O, N-R or C (R) 2 (where each group R independently represents H, a Cl8 alkyl group or an aryl group); Ph is an optionally substituted phenyl ring;

each group L independently represents a Cl6 alkenyl group or other linker group; each group Z represents a branched or linear fluorocarbon chain of up to 11 carbon atoms, preferably 3 to 9 carbon atoms; each group Y independently represents a group - (X),-Ph- (L) b-Z-CF,.

(where each of the groups X, Ph, Z and L, and each of the integers a, b and m are independently as defined above) or each group Y may represent a Cl-Cl2 alkyl or aryl, which may optionally be substituted; each a is 0 or 1; each b is 0 or 1; and each m is an integer of from 1 to 5, wherein said ligand is complexed directly or indirectly via the phosphorous moiety to a rhodium centre, for use in catalysis of hydroformylation of alkenes in a fluorous multiphase system.

By"fluorous multiphase system"we mean a system including a liquid-liquid biphase where one phase is a fluorous phase containing a fluorous solvent (typically a fluorocarbon or a fluorohydrocarbon). Suitable solvents include fluorodimethylcyclohexane, perfluoromethylcyclohexane, hexafluorobenzene, pentafluorobenzene and the like.

In one embodiment the ligand of general formula I

comprises a single fluorocarbon tail linked to a phenyl ring which is otherwise unsubstituted (apart from its connection to group X or to the phosphorous moiety).

Group Z may represent a linear group- (CFZ) n- and n is an integer of from 3 to 11. Desirably integer n represents 3,4,5,6,7,8 or 9. Generally ligands where n represents 4,5,6 or 7 are most convenient.

The fluorocarbon tail (eg.-Z-CF3) is required to adjust the solubility of the ligand in the fluorous phase.

Thus, the exact number of fluorinated carbon atoms is not fixed, but may vary according to the reactants, solvents and other reaction conditions. If a single -Z-CF3 tail is present, it may be located ortho, meta or para relative to the phosphorous linkage.

In one preferred embodiment each group Y represents a group- (X) a-Ph- (L) b-Z-CF3 m above, where X, Ph, L, b, Z and m are each as defined above.

One preferred embodiment of the ligand of the present invention is shown below in general formula Ia.

-P- {0-Ph- Z-CF, jq la (where q represents 1,2 or 3, and Ph, Z and m are each as defined above for general formula I). Preferably Z represents a linear group- (CF2) n- where n represents 4, 5,6 or 7. Preferably in formula Ia m represents 1 and q represents 3).

A protocol suitable for preparation of the ligands of general formulae I and Ia is described in Bhattacharyya et al., J. Chem. Soc., Perkin Trans. 1, pages 3609-3612 (1997). Whilst Battacharyya et al. suggest that the

ligands synthesised may be of use in a fluorous biphasic reaction, there is no suggestion that the ability of these ligands would be suitable for catalysis of alkene hydroformylation, nor that the catalysis of that reaction would provide the improved results-especially with regard to higher alkenes- now reported.

In a further aspect the present invention provides a catalyst for use in the catalysis of hydroformylation of an alkene, said catalyst comprising a ligand of general formula I (where X, Ph, n and m are as defined above).

In a preferred embodiment the ligand of said catalyst is described by general formula Ia (where n and m are as defined above, but n preferably represents 4,5,6 or 7 and m preferably represents 3).

Desirably the catalyst described above is used in the hydroformylation of higher alkenes, that is alkenes of C6 or above. Generally C6-C20 alkenes (for example Cg-C14) are of most commercial interest.

The catalyst can either be prepared in situ by addition of the phosphorous based ligand (of Formula I above) to a rhodium containing precursor. Alternatively, the catalyst may be provided as a pre-formed complex between the phosphorous ligand and rhodium. In the latter case excess phosphorous ligand may be added.

The rhodium catalytic complex may have the formula: LiaRhcLzeLafLagL5h where L1 is a ligand of formula I above and d is an integer of 1 to 6; c is an integer of 1 or more, preferably 1 to 6, most preferably c is 1 or 2; L2, L3, L4 and L5 are each ligands attached to the rhodium and may be the same or different. L2, L3, L4 and L5 may each independently represent a ligand according to formula 1 above, a halide (Cl, Br, F), a carboxylate, ß-diketonate, alkoxide, ketone, open chain or cyclic ether, water, alcohol, sulphoxide, sulphalone, amide, a sulphur donor (such as a thiol, thiolate, dialkyl sulphide, heterocycle containing S, dialkylsulphoxide, dithiocarbamate, dithiophosphonate, dithiophosphate, xanthate, dithiocarbonate); a nitrogen donor (such as an amine, amide, nitrogen containing heterocycle, imine, nitric oxide); a phosphorous donor (such as mono-or di-primary, secondary or tertiary phosphine, phosphite, phosphinite, phosphonite, phosphole or heterocycle containing phosphorous, phosphide, phosphoalkene, phosphoalkyene); arsenic donor (such as mono-or di-tertiary arsine or heterocycle containing arsenic); an antimony donor (such as stibine); a carbon donor (such as carbon monoxide, carbon dioxide, diene, triene or polyene, an alkyl or aryl goup, a carbene); a silicon donor (such as silyl or silylene group); and e, f, g and h are each, independently, an integer of from 0 to 6.

Any of ligands L2, L3, L4 and Ls may be joined to each other by a suitable bridging group.

A reference to a"rhodium containing precursor"refers to a catalytic complex as described above to which a phosphorous ligand of formula I is to be added. The rhodium containing precursor may be of formula: Rh L2L3L4L5 where c, e, f, and h are as defined above, but e+f+g+h=1 or more; and L2, L3, L'and L'are as defined above.

Optionally, the ligand of formula I may displace an existing ligand attached to the rhodium centre.

In a further aspect the present invention provides a process for hydroformylation of alkenes in a fluorous multiphase system, said process comprising the step of adding a catalyst including a ligand of general formula I to the reactants.

In an alternative embodiment the present invention provides a process for hydroformylation of alkenes in a fluorous multiphase system, said process comprising the step of adding a ligand of formula I above and a rhodium precursor (as described above) to produce a catalyst in situ.

Desirably the ligand is described by general formula Ia.

Optionally, the process relates to hydroformylation of higher (eg C6 and above) alkenes, for example C6-C20 alkenes. Cg-C14 alkenes are of most commercial

interest.

In one embodiment the P: Rh ratio is 20: 1 or lower, preferably 12: 1 or lower, for example 6: 1 or even as low as 3: 1.

Optionally the process further includes the step of recovering the catalytic complex by separating the fluorous phase from the phase containing the reaction products.

The present invention will now be described further with reference to the following, non-limiting, examples. (Examples 1 to 5 inclusive are comparative Examples.) Examples All reactions were carried out in a mechanically stirred Hastelloy C autoclave fitted with a ballast vessel from which gas was metered into the reaction autoclave via a mass-flow controller so as to maintain a constant pressure within the reaction autoclave. The rate of reaction was measured by monitoring the rate of pressure drop within the ballast vessel.

Examples 1-12: Hvdroformylation of Hex-1-ene The solvents, rhodium complex and phosphorous containing compound were introduced in the autoclave under argon. CO/H2 (total pressure 13 bar) was introduced and the autoclave heated with stirring to the reaction temperature. Hexene was contained in an injection unit between the autoclave and the mass flow controller. Once the conditions in the autoclave had stabilised, the tap between the injector and the autoclave was opened and gas from the ballast vessel

allowed to pass through the mass flow controller to inject the hexene into the autoclave and bring the pressure in the autoclave to 20 bar. Readings of the pressure in the ballast vessel and the autoclave were taken every 5 seconds for approximately 1 hour. A typical reaction profile is shown in Figure 1.

From the results in Table 1 it is clear that P (OC6H4-4-C6F13) 3 and P (OC6H4-3-C6F13) 3 have considerable benefits over other ligands studied with high reaction rates and good n: i ratio at a P: Rh ration of 3: 1.

Visual inspection of the resulting two phase mixture showed that the top (organic) phase was colourless whilst the lower (fluorous) phase was yellow in colour. Analytical data on the rhodium content of the organic phase is currently being obtained.

The results, collected in Table 1, were obtained under the following conditions (unless otherwise stated): [Rh (acac) (CO) 2] (0.01 mol dm~3), phosphine (0.03 mol dm-3), hex-1-ene (1 cm3) in a mixture of toluene (2 cm3) and PP3 (2 cm3), 70°C, 20 bar, 1 hour.

TABLE 1. Hydroformylation of hex-1-ene catalysed by rhodium complexes Example Ligand hex- isom/ 2EtP/ 2MeH/ H/% Conversion Selectivity n:i Initial 1- % % % /% to TOF/s-1 ene/% aldehyde/% 1 PPh3a 0.8 6.1 1.9 23.2 67.9 99.2 93.9 2.7 0.25 2 PPh3a 0.4 3.9 6.4 21.2 68.1 99.6 96.1 2.5 0.25 3 PPh3 1.0 1.8 0.3 23.7 73.3 99.0 98.2 3.1 0.32 4 P(C6H4C6F13)3 1.7 10.6 0.9 17.3 69.6 98.3 89.2 3.8 1.3 5 P(OPh)3 0.4 8.0 4.1 19.6 67.9 99.6 92.0 2.9 0.48 6 P(OC6H4-4-C6F13)3 0.3 17.7 1.4 9.7 70.9 99.7 82.3 6.4 0.99 7 P(OC6H4-4-C6F13)3 0.8 14.6 0.7 8.3 75.6 99.2 85.3 8.4 0.74 8 P(OC6H4-4-C6F13)3c 1.4 9.3 3.2 18.6 67.5 98.6 90.6 3.1 0.29 9 P(OC6H4-4-C6F13)3d 0.3 10.7 1.4 10.3 77.2 99.7 89.3 6.6 0.51 10 P(OC6H4-3-C6F13)3 0.1 3.9 2.5 12.9 80.6 99.9 96.1 5.2 0.26 11 P(OC6H4-2-C6F13)3 0.1 0.8 14.5 39.1 45.5 99.9 99.2 0.9 14.0 12 P(OC6H4-4-C6F13)2 25.7 14.6 0.2 15.8 43.7 74.3 80.4 2.7 0.24 -(CF=CF2) lisom=isomerised hexenes, 2EtP=2-ethylpentanal, 2MeH=2-methylhexanal, H=heptanal, TOF=turnover<BR> (moles of hex-1-ene consumed per mol of rhodium per second); n:i=ratio of straight to total br<BR> a In toluene (4 cm3);<BR> b Zero order throughout most of the reaction;<BR> c [Rh(acac) (CO)2] (0.001 mol dm-3), P(OC6H4-4-C6F13)3(0.003 mol dm-3);<BR> d P=8 bar.<BR> <P>Conditions (unless otherwise stated): [Rh(acac)(CO)2] (0.01 mol dm-3), phosphine (0.03 mol dm-3<BR> hex-1-ene (1 cm3) in a mixture of toluene (2 cm3) and PP3 (2 cm3), 70°C, 20 bar, 1 hour.

Examples 13-16: Hydroformylation of Nonenes The procedure of Examples 1-12 was followed, using either 1-nonene or 2-nonene as substrate.

The results, collected in Table 2, were obtained under the following conditions (unless otherwise stated): moldm-3),P[OC6H4-4-C6F13)3(0.03[Rh(acac)(CO)2](0.01 mol dom-3), nonene (1 cm3) in a mixture of toluene (2 cm3) and PP3 (2 cm3), 70°C, 20 bar, 1 hour.

TABLE 2. Hydroformylation of Nonenes Example 1-nonene 2-nonene 3- and 2PrH/ 2EtO/ 2MeN D/% Conversion Selectivity % % 4- % % /% /% to nonene Aldehydes/% % 13a 1.0 12.8 1.2 - 1.0 9.8 74.2 99.0 85.9 14b 0.2 11.8 20.3 7.3 12.0 33.0 15.4 88.2 76.8 15b,c 0.2 13.9 11.0 7.2 17.8 39.5 10.4 86.1 87.0 16b,c,d 0.4 21.0 38.7 4.2 5.2 16.3 14.2 79.0 50.5 2PrH=2 propylhexanal, 2EtO=2-ethyloctanal, 3MeN=2-methylnonanal, D=decanal.<BR> a 1-nonene as substrate;<BR> b 2-nonene as substrate;<BR> c P=8 bar;<BR> d T=90°C.<BR> <P>Conditions (unless otherwise stated) : [Rh(acac) (CO)2] (0.01 mol dm-3), P(C6H4-4-C6F13)3 (0.03 mol<BR> cm3) in a mixture of toluene (2 cm3) and PP3 (2 cm3), 70°C, 20 bar, 1 hour.