A METHOD OF SYNTHESISING A PT(II) COMPLEX; A PT(II) COMPLEX; USE OF SUCH A COMPLEX AS A PHOTOACTIVATABLE CATALYST IN A HYDROSILYLATION REACTION

Abstract

A method of synthesising a Pt(II) complex includes a first step of preparing a reaction mixture comprising a water-soluble hexachloroplatinate salt and a compound according to Formula I′, or salt thereof, and allowing the water-soluble hexachloroplatinate salt and the compound according to Formula I′ to react and a second step of adding a further quantity of the compound according to Formula I′, or a salt thereof, to the reaction mixture. Products of this method are Pt(II) complexes according to Formula I The Pt(II) complexes are useful as catalysts in hydrosilylation reactions.

##STR00001##

Claims

1. A method of synthesising a Pt(II) complex comprising: (i) a first step of preparing a reaction mixture comprising a water-soluble hexachloroplatinate salt and a compound according to Formula I′, or salt thereof, and allowing the water-soluble hexachloroplatinate salt and the compound according to Formula I′ to react ##STR00009## wherein X is selected from OH, SH and NH.sub.2, and Y and Z, together with the two carbon atoms to which they are attached, form a 4- to 12-membered aromatic or heteroaromatic group optionally substituted with one or more groups R.sup.1, wherein R.sup.1 is independently selected from linear or branched C.sub.1-6 alkyl, optionally substituted by one or more groups R.sup.2, F, Cl, Br, CN, OH, OR.sup.3, NH.sub.2, NHR.sup.4, NR.sup.4.sub.2, NO.sub.2, NHCOH, NHCOR.sup.5, COH, CO.sub.2H, CO.sub.2R.sup.5, COR.sup.5, OCOH, OCOR.sup.5, CONH.sub.2, CONHR.sup.4, CONR.sup.4.sub.2 and SO.sub.3H, R.sup.2 is independently selected from F, Cl, Br and OH, and each of R.sup.3, R.sup.4 and R.sup.5 are independently selected from linear or branched unsubstituted C.sub.1-6 alkyl; and (ii) a second step of adding a further quantity of the compound according to Formula I′, or a salt thereof, to the reaction mixture.

2. The method of claim 1, further comprising an intermediate step, after the first step but before the second step, of adding a reducing agent to the reaction mixture.

3. The method of claim 1, wherein in the first step the compound according to Formula I′ is used in stoichiometric excess.

4. The method of claim 1, wherein in the first step the reaction mixture further comprises a solvent selected from water or water mixed with an alcohol.

5-7. (canceled)

8. The method of claim 1, wherein the water-soluble hexachloroplatinate salt is selected from Na.sub.2[PtCl.sub.6] and chloroplatinic acid.

9. The method of claim 1, wherein the first step further comprises leaving the reaction mixture to react for at least 10 minutes before any further step is carried out.

10. (canceled)

11. The method of claim 1, wherein the compound according to Formula I′ and the water-soluble hexachloroplatinate salt are added to the reaction mixture in the first step in a molar ratio of at least 2:1.

12. The method of claim 2, wherein the reducing agent added in the intermediate step is an alcoholic reducing agent.

13. The method of claim 2, wherein the intermediate step comprises heating the reaction mixture to a temperature of at least 50° C. and allowing the mixture to remain at this temperature for at least 2 hours.

14-15. (canceled)

16. The method of claim 1, wherein Y and Z, together with the two carbon atoms to which they are attached, form a 4- to 8-membered aromatic or heteroaromatic group optionally substituted with one or more groups R.sup.1.

17. The method of claim 16, wherein Y and Z, together with the two carbon atoms to which they are attached, form an unsubstituted 4- to 8-membered aromatic or heteroaromatic group.

18. The method of claim 17, wherein Y and Z, together with the two carbon atoms to which they are attached, form an unsubstituted 6-membered aromatic group.

19. The method of claim 1, wherein the compound according to Formula I′ is salicylaldehyde.

20. A Pt(II) complex according to Formula I ##STR00010## wherein X′ is selected from O, S and NH, and Y and Z, together with the two carbon atoms to which they are attached, form a 4- to 12-membered aromatic group optionally substituted with one or more groups R.sup.1 or a 4- to 12-membered heteroaromatic group substituted with at least one group R.sup.1; wherein R.sup.1 is independently selected from linear or branched C.sub.1-6 alkyl, optionally substituted by one or more groups R.sup.2, F, Cl, Br, CN, OH, OR.sup.3, NH.sub.2, NHR.sup.4, NR.sup.4.sub.2, NO.sub.2, NHCOH, NHCOR.sup.5, COH, CO.sub.2H, CO.sub.2R.sup.5, COR.sup.5, OCOH, OCOR.sup.5, CONH.sub.2, CONHR.sup.4, CONR.sup.4.sub.2, SO.sub.3H, wherein R.sup.2 is independently selected from F, Cl, Br and OH, wherein each of R.sup.3, R.sup.4 and R.sup.5 are independently selected from linear or branched unsubstituted C.sub.1-6 alkyl.

21. (canceled)

22. The Pt(II) complex of claim 20, wherein Y and Z, together with the two carbon atoms to which they are attached, form a 4- to 8-membered aromatic group optionally substituted with one or more groups

23-25. (canceled)

26. A method of performing a hydrosilylation reaction catalysed by a Pt(II) complex according to Formula I: ##STR00011## wherein X′ is selected from O, S and NH, and Y and Z, together with the two carbon atoms to which they are attached, form a 4- to 12-membered aromatic or heteroaromatic group optionally substituted with one or more groups R.sup.1; wherein R.sup.1 is independently selected from linear or branched C.sub.1-6 alkyl, optionally substituted by one or more groups R.sup.2, F, Cl, Br, CN, OH, OR.sup.3, NH.sub.2, NHR.sup.4, NR.sup.4.sub.2, NO.sub.2, NHCOH, NHCOR.sup.5, COH, CO.sub.2H, CO.sub.2R.sup.5, COR.sup.5, OCOH, OCOR.sup.5, CONH.sub.2, CONHR.sup.4, CONR.sup.4.sub.2, SO.sub.3H, wherein R.sup.2 is independently selected from F, Cl, Br and OH, wherein each of R.sup.3, R.sup.4 and R.sup.5 are independently selected from linear or branched unsubstituted C.sub.1-6 alkyl.

27. The method of claim 26, wherein the hydrosilylation reaction is photoactivated.

28. (canceled)

29. The method of claim 26, which comprises cross-linking of a siloxane polymer or copolymer.

30. (canceled)

31. A curable composition comprising a Pt(II) complex according to Formula I: ##STR00012## wherein X′ is selected from O, S and NH, and Y and Z, together with the two carbon atoms to which they are attached, form a 4- to 12-membered aromatic or heteroaromatic group optionally substituted with one or more groups R.sup.1; wherein R.sup.1 is independently selected from linear or branched C.sub.1-6 alkyl, optionally substituted by one or more groups R.sup.2, F, Cl, Br, CN, OH, OR.sup.3, NH.sub.2, NHR.sup.4, NR.sup.4.sub.2, NO.sub.2, NHCOH, NHCOR.sup.5, COH, CO.sub.2H, CO.sub.2R.sup.5, COR.sup.5, OCOH, OCOR.sup.5, CONH.sub.2, CONHR.sup.4, CONR.sup.4.sub.2, SO.sub.3H, wherein R.sup.2 is independently selected from F, Cl, Br and OH, wherein each of R.sup.3, R.sup.4 and R.sup.5 are independently selected from linear or branched unsubstituted C.sub.1-6 alkyl.

32. The curable composition of claim 31, which is a curable silicone composition.

33. A cured silicone product formed by curing the curable composition claim 32.

34. cured silicone product of claim 33, which is an elastomer, a lens, a coating or on an electronic component, a cured adhesive or a dental impression.

35. (canceled)

Description

FIGURES

[0224] FIG. 1 is a plot of an infra-red spectrum taken from the product of Example 1.

[0225] FIG. 2 is a plot of an X-ray photoelectron spectrum taken from the product of Example 1.

[0226] FIG. 3 shows the crystal structure of the product of Example 3.

[0227] FIG. 4 shows a UV/Vis spectrum taken from the product of Example 3.

[0228] FIG. 5 shows a UV/Vis spectrum taken from various samples.

[0229] FIG. 6 shows a fluorescence spectrum for a siloxane polymer.

[0230] FIG. 7 shows fluorescence spectra for the product of Example 3, in acetone and in siloxane.

[0231] FIG. 8 shows fluorescence spectra for Pt(acac).sub.2, in acetone and in siloxane.

[0232] FIG. 9 shows a TGA trace for the product of Example 3.

[0233] FIG. 10 is a .sup.1H NMR spectrum on the product of Example 2.

[0234] FIG. 11 shows the same spectrum as FIG. 10 on a different scale.

[0235] FIG. 12 is a .sup.1H NMR spectrum on the product of Example 2.

[0236] FIG. 13 is a .sup.195Pt NMR spectrum on the product of Example 2.

EXAMPLES

Comparative Example 1

[0237] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to deionised water (70 mL) and a mixture of salicylaldehyde (2.45 mL, 2.8 g, 22.8 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in EtOH (15 mL) was then added. The reaction mixture was heated under reflux with stirring for 1 hour. The colour changed from bright orange to red.

[0238] The solution was then allowed to cool naturally to room temperature. An orange oil has separated from an orange aqueous layer. A small amount of orange precipitate was observed on the surface. The precipitate was collected and products were isolated from the organic and aqueous layers. The precipitate was found by NMR analysis to contain no organic material, and was presumably unreacted Na.sub.2PtCl.sub.6. The products in the organic and aquous layers were analysed by IR but found not to contain the desired product.

Comparative Example 2

[0239] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to deionised water (70 mL) and a mixture of salicylaldehyde (2.45 mL, 2.8 g, 22.8 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in EtOH (10 mL) was then added giving a bright orange solution with a small amount of whitish oil. The reaction mixture was heated under reflux at 100° C. for 5 hours before being allowed to cool to room temperature. Full reduction to platinum black occurred and the reaction was abandoned.

Comparative Example 3

[0240] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to deionised water (50 mL) and a mixture of salicylaldehyde (2.45 mL, 2.8 g, 22.8 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in EtOH (10 mL) was then added. The reaction mixture was heated at 90° C. under stirring for 16 hours. The platinum underwent full reduction to platinum black and the reaction was abandoned.

Comparative Example 4

[0241] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.925 mL, 1.06 g, 8.68 mmol) and NaHCO.sub.3 (1.09 g, 13.02 mmol) in EtOH (50 mL). The reaction mixture was heated at 80° C. under stirring. After 30 mins the colour remained orange, but full reduction to platinum black occurred after 1 hour and the reaction was abandoned.

Comparative Example 5

[0242] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.925 mL, 1.06 g, 8.68 mmol) and NaHCO.sub.3 (1.09 g, 13.02 mmol) in EtOH (50 mL). The reaction mixture left stirring at room temperature for 2 days. The reaction mixture was then filtered to remove a white precipitate from a bright orange solution. The solvent was allowed to evaporate from the bright orange solution which then separated into two components, a small amount of brown solution and a bright orange solution.

[0243] The bright orange solution was miscible in water and suspected to be unreacted H.sub.2PtCl.sub.6.

[0244] The brown solution gave an orange oil which was tested for catalytic activity in gelling of a siloxane polymer. No catalytic activity was observed.

Comparative Example 6

[0245] A 16.13 wt % aqueous solution of Pt(IV) nitrate (2.624 g, 2.17 mmol) was added to deionised water (50 mL) and a mixture of salicylaldehyde (2.45 mL, 2.8 g, 22.8 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in EtOH (15 mL) was then added. The reaction mixture gave off gas and produced an orange precipitate. Stirring was continued at room temperature for 2 hours. The reaction mixture was then filtered to give an orange precipitate and an orange solution. The precipitate was washed with water and diethylether. The product showed no solubility in toluene, dichloromethane, MIBK or acetone. The product was tested for catalytic activity but none was found. XPS analysis was performed which showed that little reduction of the platinum took place and the desired product was not formed. The major product appeared to be Pt.sup.IV(HCO.sub.3).sub.4.

Comparative Example 7

[0246] A reaction was performed as in Comparative Example 6, except that no base (NaHCO.sub.3) was added. The product characteristics were the same as for Comparative Example 6.

Comparative Example 8

[0247] Hexahydroxyplatinic acid, H.sub.2Pt(OH).sub.6 (0.661 g, 2.17 mmol) was stirred in deionised water (50 mL). To this a mixture of salicylaldehyde (2.45 mL, 2.8 g, 22.8 mmol) in EtOH (15 mL) was then added. The H.sub.2Pt(OH).sub.6 starting material was not soluble in water and formed a pale yellow/white suspension. No change occurred on addition of the salicylaldehyde. NaHCO.sub.3 (0.765 g, 9.12 mmol) was added to the reaction mixture, which turned yellow but still contained the pale precipitate. The mixture was heated at 103° C. for 30 mins. Full reduction of the platinum to a dark brown/black precipitate occurred and the reaction was abandoned.

Comparative Example 9

[0248] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (10 mL). The reaction mixture was stirred at room temperature for 24 hours. 37% aqueous formaldehyde solution (0.323 mL, 0.352 g, 4.34 mmol) in 10 mL water was added to the reaction mixture. The reaction mixture was heated at 93° C. with stirring for 5 hours. The colour gradually changed from yellow to red/orange, but then the platinum underwent full reduction to Pt(0). The reaction was abandoned.

Comparative Example 10

[0249] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (10 mL). The reaction mixture was stirred at room temperature for 24 hours. Oxalic acid dehydrate (0.137 g, 1.09 mmol) was added to the reaction mixture and the mixture was heated to 93° C. and stirred for 6 hours. The colour gradually changed from yellow to orange to red but no precipitate was formed. The mixture was left to stand at room temperature for 3 days, after which time a very small amount of orange precipitate appeared to have formed. The mixture was heated again and turned black. The reaction was abandoned.

Comparative Example 11

[0250] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (10 mL). Stirring was continued at room temperature overnight.

[0251] 2-hydroxybenzylalcohol (0.269 g, 2.17 mmol) in EtOH (20 mL) was added and the reaction mixture was heated to 73° C. After 1.5 hours the reaction mixture had turned from a yellow colour to a dark orange, but no precipitate had occurred. The reaction was abandoned.

Example 1

[0252] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (10 mL). The reaction mixture was stirred overnight at room temperature.

[0253] Salicylaldehyde (2 mL, 2.28 g, 18.62 mmol) in EtOH (20 mL) was added and the reaction mixture was heated to 93° C. and held at that temperature for 5 hours. The reaction mixture was then allowed to cool naturally to room temperature and it was observed that an orange precipitate had formed. The precipitate was collected by filtration, leaving a yellow filtrate.

[0254] The yield was 57 mg of product (6%).

[0255] IR and XPS spectra were obtained for the product, confirming that it was the desired product according to Formula A below. The IR and XPS spectra are shown in FIGS. 1 and 2 respectively.

##STR00008##

[0256] Based on the XPS results, the elemental analysis was estimated as follows:

TABLE-US-00001 Element Amount (at %) C 74.7 O 20.2 Pt 4.5 Cl 0.5 Na 0.2

[0257] The carbon 1s signal contains two main signals, the main signal appears at 285 eV (used for the binding energy scale correction) and is assigned to alkyl functions. The satellite feature at −291 eV is indicative of an aromatic species. The peak at −287 eV is due to carbon-oxygen functions.

[0258] The XPS shows that reduction to Pt(II) has taken place. There are very small amounts of residual Cl and Na. The ratio of carbon and oxygen to Pt is slightly higher than would be expected, suggesting the presence of some residual HCO.sub.3.sup.−.

[0259] CHN elemental analysis was also carried out using a CEE-440 Elemental Analyzer from Exeter Analytical Inc.

[0260] Pt elemental analysis was carried out using ICP. Microwave digestion was carried out in 10 mL reverse Aqua Regia in quartz vessels. Solutions were made up in 100 mL volumetric flasks with the addition of yttrium as an internal standard. Samples were run on an Agilent ICP-OES 5110 SVDV instrument.

[0261] The results are shown below:

TABLE-US-00002 Element Amount (wt %) C 39.0 H 2.39 N 0.08 Pt 42.6

[0262] The ratio of C:H is 1.4:1, which is as expected for the singly deprotonated salicylaldehyde ligand. The CHN analysis fits with that expected for two deprotonated salicylaldehyde ligands per Pt.

Example 2

[0263] The reaction in Example 1 was repeated, except that after the addition of salicylaldehyde the mixture was heated at a lower temperature of 73° C. for a longer period (overnight). Some orange precipitate was formed and was collected by filtration.

[0264] The yield of product was 70 mg (7.4%).

Example 3

[0265] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (10 mL). The reaction mixture was stirred overnight at room temperature.

[0266] EtOH (20 mL) was added and the reaction mixture was heated to 83° C. and held at that temperature for 6 hours. The mixture was then allowed to cool to room temperature and stirred at room temperature overnight. The colour had changed to orange and a very small amount of precipitate had occurred.

[0267] Salicylaldehyde (1 mL, 9.3 mmol) and NaHCO.sub.3 (0.78 g, 9.28 mmol) in deionised water (10 mL) was added to the reduced reaction mixture and the temperature was raised again to 83° C. and held at that temperature. After 1 hour a product had begun to precipitate. After 2 hours this product was collected by filtration.

[0268] The product yield was 0.305 g (32.1%).

[0269] Comparing the yields of Example 3 with those of Examples 1 and 2, it can be seen that performing an intermediate reduction step with ethanol, followed by a distinct subsequent step in which more salicylaldehyde is added, drives the formation of the product in higher yield.

Example 4

[0270] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of excess salicylaldehyde (1 mL, 9.3 mmol) and NaHCO.sub.3 (0.78 g, 9.28 mmol) in deionised water (100 mL) and EtOH (10 mL). The reaction mixture was stirred overnight at room temperature.

[0271] EtOH (20 mL) was added and the reaction mixture was heated to 83° C. After 3 hours the reaction mixture had turned bright orange but there was no sign of precipitate. The pH was tested and was found to be around 7.

[0272] Salicylaldehyde (1 mL, 9.3 mmol) and NaHCO.sub.3 (0.78 g, 9.28 mmol) in deionised water (10 mL) was added to the reaction mixture and the temperature was raised again to 83° C. and held at that temperature. After 2 hours a small amount of product had begun to precipitate. The reaction mixture was stirred at room temperature overnight yielding more precipitate. The temperature was raised to 83° C. again for four hours and then allowed to cool to room temperature and the precipitate collected by filtration through 541 paper.

[0273] The product yield was 0.406 g (42.8%).

[0274] The use of ethanol alone during the reduction step followed by the addition of excess salicylaldehyde during a further step drives the formation of the product in much higher yield. The use of a large excess of salicylaldehyde in the initial reaction with H.sub.2PtCl.sub.6 also seems to contribute to the increased product yield.

Example 5

[0275] In this Example the synthesis method of Example 4 was carried out at double scale to produce a larger quantity of product and test the scalability of the method.

[0276] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (3.38 g, 4.34 mmol) was added to a mixture of salicylaldehyde (2 mL, 18.6 mmol) and NaHCO.sub.3 (1.56 g, 18.6 mmol) in deionised water (200 mL) and EtOH (20 mL). Stirring was continued at room temperature overnight.

[0277] EtOH (40 mL) was added and the reaction mixture was heated at 83° C. for 4 hours.

[0278] A further solution of salicylaldehyde (2 mL, 18.6 mmol) and NaHCO.sub.3 (1.56 g, 18.6 mmol) in deionised water (20 mL) was added and heating was continued for another 2 hours. The reaction mixture was then left stirring at room temperature overnight. The temperature was raised to 83° C. again for another 4 hours before the reaction mixture was allowed to cool to room temperature and the product collected by filtration through 541 paper.

[0279] The yield of product (denoted ‘Product A’) at this stage was 0.720 g.

[0280] The filtrate was heated for a further 6 hours, yielding more precipitate, which was collected in the same way.

[0281] The yield of product (denoted ‘Product B’) at this stage was 0.130 g.

[0282] The total yield of Products A and B was 0.850 g (44.8%).

[0283] It is clear that the process can be scaled up to double the quantity without any adverse effect on product yield.

Example 6

[0284] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL). The yellow reaction mixture turned an even brighter shade of yellow on addition of the platinum starting material. There still appeared to be some immiscible droplets of salicylaldehyde present, but no precipitate occurred.

[0285] EtOH (10 mL) was then added. Stirring was continued at room temperature overnight.

[0286] After stirring overnight there was no evidence of hydrolysis of the platinum—the colour remained yellow.

[0287] Salicylaldehyde (1 mL, 1.14 g, 9.31 mmol) in EtOH (10 mL) was added to a 55 mL quantity of the reaction mixture and the reaction mixture was heated at reflux for 5 hours, then allowed to cool and stirred at room temperature overnight. The yellow colour became a deeper more orange shade and a red/orange oil became separated from the solution. The oil was soluble in dichloromethane. 60 mL of this was used to separate it from the remaining lighter orange aqueous layer. The organic layer was allowed to evaporate leaving a precipitate (‘Product 6A’).

[0288] The yield was 35%.

[0289] The precipitate appeared to be made up of two components—an orange powder and a brown powder. It is possible that the brown powder is formed due to hydrolysis when in contact with the water, or from formation of multi-nuclear species once concentrated.

Example 7

[0290] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and isopropanol (10 mL). Stirring was continued at room temperature overnight.

[0291] Isopropanol (20 mL) was added and the reaction mixture was heated at 83° C. for 4 hours.

[0292] A further solution of salicylaldehyde (1 mL, 9.3 mmol) and NaHCO.sub.3 (0.78 g, 9.28 mmol) in deionised water (10 mL) was added and heating was continued for another 3 hours. No precipitate had occurred during this time, but after leaving at room temperature overnight heating was continued at 83° C. for a further 6 hours, after which the reaction mixture was allowed to cool to room temperature and the orange precipitate collected by filtration through 541 paper. It was washed with more deionised water and then dried in a vacuum oven at 40° C. overnight.

[0293] The yield was 0.283 g (29.8%).

[0294] This shows that isopropanol is equally useful as a reducing agent as an alternative to ethanol, without requiring any more work-up.

Example 8

[0295] This Example was carried out to investigate the effect of varying the quantity of salicylaldehyde added in the second step of the reaction.

[0296] Method A—No Further Salicylaldehyde Addition

[0297] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (10 mL). Stirring was continued at room temperature for 15 minutes.

[0298] EtOH (20 mL) was added and the reaction mixture was heated at 83° C. for 4 hours.

[0299] No additions were made to the reaction mixture at this point and heating was continued for a further 3 hours. After leaving at room temperature overnight heating there was no sign of any precipitate. Heating was continued at 83° C. for a further 5 hours as standard. The reaction mixture turned black indicating that full reduction to Pt(0) had taken place.

[0300] Method B—Addition of 0.5 mL Further Salicylaldehyde

[0301] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (10 mL). Stirring was continued at room temperature for 15 minutes.

[0302] EtOH (20 mL) was added and the reaction mixture was heated at 83° C. for 4 hours.

[0303] Salicylaldehyde (0.5 mL, 4.65 mmol) in deionised water (10 mL) with NaHCO.sub.3 (0.39 g, 4.64 mmol) was added to the reduced reaction mixture and heating was continued for a further 3 hours. After leaving at room temperature overnight heating was continued at 83° C. for a further 5 hours, after which the reaction mixture was allowed to cool to room temperature and the orange precipitate collected by filtration through 541 paper. It was washed with more deionised water and then dried in a vacuum oven at 40° C. overnight.

[0304] The yield was 0.276 g (29.1%).

[0305] Method C—Addition of 2 mL Further Salicylaldehyde

[0306] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (10 mL). Stirring was continued at room temperature for 15 minutes.

[0307] EtOH (20 mL) was added and the reaction mixture was heated at 83° C. for 4 hours.

[0308] Salicylaldehyde (2 mL, 18.6 mmol) in deionised water (20 mL) with NaHCO.sub.3 (1.56 g, 18.56 mmol) was added to the reduced reaction mixture and heating was continued for a further 3 hours. After leaving at room temperature overnight heating was continued at 83° C. for a further 5 hours, after which the reaction mixture was allowed to cool to room temperature.

[0309] The yield was 0.342 g (36%).

Example 9

[0310] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of salicylaldehyde (0.49 mL, 0.56 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (10 mL). Stirring was continued at room temperature for 60 hours giving a yellow solution. A sample was taken at this point for TLC analysis.

[0311] An excess of salicylaldehyde (2 mL, 2.28 g, 18.62 mmol) in EtOH (20 mL) was added and the reaction mixture was heated at 73° C. overnight. The reaction mixture changed from yellow to orange and an orange precipitate was formed. There also appeared to be an oily orangy-yellow material which made collection of the precipitate by filtration more difficult. It was therefore washed with MeOH, in which the product appeared to be only very slightly soluble. No further material was collected from the MeOH washings.

[0312] The yield was 83 mg (8.75%).

[0313] TLC Analysis

[0314] TLC was carried out on the reaction mixture after the first room temperature step, CPA, salicylaldehyde (in EtOH) and the sodium salt of salicylaldehyde (in EtOH). Silica TLC plates were used with a mobile phase of 80:20 DCM:pentane.

[0315] CPA: R.sub.f=0

[0316] Salicylaldehyde: R.sub.f=0.85

[0317] Salicylaldehyde+NaHCO3: R.sub.f=0.85

[0318] Fresh reaction mixture before heating: R.sub.f=0; R.sub.f=0.65

[0319] Reaction mixture after first step: R.sub.f=0; R.sub.f=0.65

[0320] TLC does not suggest that extending the first step makes any difference to how near completion that step is, however the ease of reduction of the reaction mixture in the second step suggests that there is a difference in the speciation; there could be a difference in the ratios of the two spots present that is not seen in the TLC.

Example 10

[0321] A 25 wt % aqueous solution of H.sub.2PtCl.sub.6 (1.69 g, 2.17 mmol) was added to a mixture of 2-hydroxy-1-naphthaldehyde (0.785 g, 4.56 mmol) and NaHCO.sub.3 (0.765 g, 9.12 mmol) in deionised water (100 mL) and EtOH (20 mL). The reaction mixture was stirred overnight at room temperature.

[0322] EtOH (10 mL) was added and the reaction mixture was heated to 83° C. and held at that temperature for 6 hours. The mixture was then allowed to cool to room temperature and stirred at room temperature overnight. An orange/red precipitate was observed.

[0323] 2-Hydroxy-1-naphthaldehyde (1.6 g, 9.3 mmol), EtOH (20 mL) and NaHCO.sub.3 (0.78 g, 9.28 mmol) were added to the reduced reaction mixture and the temperature was raised again to 83° C. and held at temperature for 5 hours. The reaction mixture was allowed to cool to room temperature resulting in further precipitation. This was collected by filtration.

[0324] It was observed that the precipitate comprises a mixture of red and orange species; the desired product and unreacted 2-hydroxy-1-naphthaldehyde, respectively. The product was washed with deionised water and diethyl ether to remove excess ligand.

[0325] The yield was 324 mg (27.8%).

[0326] Crystal Growth

Example 11

[0327] Crystals of the product of Example 3 were grown as single crystals for analysis.

[0328] The following different methods were attempted in order to provide suitable crystals for testing. [0329] 1. Growth in acetone/water medium. This resulted in mixing of the two solvents and fast precipitation of the bright orange product. [0330] 2. Growth in DCM/hexane. This formed two distinct layers with slow mixing occurring at the interface. After being left for one week, it was found that some very small crystals had been deposited on the glass vessel in the upper layer, but the majority was deposited at the bottom of the flask and appears to have turned more brown in colour. It is thought that the product is not completely stable in dichloromethane. [0331] 3. Growth in chloroform/hexane. This formed two distinct layers with slow mixing occurring at the interface. Slightly larger crystals were formed, but still too small. It took longer for the product to turn brown. [0332] 4. Growth in chloroform: The product was dissolved in chloroform with heating, and immediately filtered before being stored in the freezer. Needle like crystals were formed [0333] 5. Growth in chloroform/hexane in freezer. Needle like crystals were formed

[0334] The crystal strcture was determined and is shown in FIG. 3. It is triclinic with space group P-1. The results show that the product has the expected structure of two bidentate salicylaldehyde ligands coordinated to a central Pt atom through the oxygen atoms.

[0335] IR and NMR

Example 12

[0336] NMR spectroscopy was performed in CDCl.sub.3 for the product of Example 2. The .sup.195Pt spectrum is shown in FIG. 13. It has a single peak at 4371 ppm. This shows that there is a single Pt species present. It is in the region where a peak representing Pt(II) with four coordinated oxygen would be expected to occur, and there is no sign of the starting material (or variants).

[0337] .sup.1H NMR (shown in FIGS. 10 and 11) and .sup.13C (shown in FIG. 12) spectra were also collected.

[0338] UV/Vis Spectroscopy

Example 13

[0339] A UV/Vis spectrum was gathered for the complex made in Example 3 in toluene and is shown in FIG. 4. The spectrum shows three main peaks: 468 nm, 349 nm and 283 nm. There was no absorbance above 530 nm.

[0340] UV/Vis spectra were also gathered for the complex in various other solvents and compared with results for Pt(acac).sub.2. The results are shown in FIG. 5.

[0341] Fluorescence

Example 14

[0342] Fluorescence measurements were carried out on a Cary Eclipse Spectrometer.

[0343] Five different samples were studied: [0344] 1. Vinyl-terminated polydimethylsiloxane 100 cSt [0345] 2. 1 mg/mL of the Pt complex (product of Example 1) in acetone (note: saturated solution, prone to some precipitation) [0346] 3. 1 mg/mL of the Pt complex (product of Example 1) in vinyl-terminated polydimethylsiloxane (note: poor solubility, solution very cloudy and prone to precipitation). [0347] 4. 1 mg/mL Pt(acac).sub.2 in acetone (note: fully soluble) [0348] 5. 1 mg/mL Pt(acac).sub.2 in vinyl-terminated polydimethylsiloxane (note: poor solubility, solution cloudy and prone to precipitation).

[0349] The results are shown in FIGS. 6-8.

[0350] FIG. 6 shows that the siloxane itself does show some fluorescence. The emission wavelength was scanned with an excitation of 300 nm and showed a maximum emission intensity of 268 at 380 nm. The excitation was then scanned with the emission held at 380 nm, showing a maximum intensity of 329 at 316 nm.

[0351] FIG. 7 shows that the Pt(II) complex is fluorescent. In acetone with an excitation wavelength of 190 nm there is a sharp emission peak at 540 nm with an intensity of 784. Holding the emission at 540 nm and scanning the excitation gives a peak at 190 nm (scanning was not carried out below this wavelength).

[0352] FIG. 7 also shows that the emission spectrum of the Pt(II) complex looks different in siloxane. When excited at 190 nm there is still a peak at in emission at 540 nm with intensity of 742, however there are also emission peaks at lower wavelengths: 491 nm (intensity 407) and 420 nm (intensity 385). These may be due to interaction with the siloxane. When excited at 300 nm (as in the siloxane only sample) only a weak emission is recorded (intensity approx. 50 between 330 and 380 nm); this is much less intense than the peak at 380 nm recorded in the siloxane only sample. When the emission is held at 380 nm (as in the siloxane only sample) the excitation shows a peak at 190 nm and at 295 nm (lower wavelength than that expected for the siloxane) again hinting at interaction between the complex and solvent.

[0353] FIG. 8 shows that for Pt(acac).sub.2 in acetone when excited at 190 nm the emission spectrum shows a peak at 489 nm with intensity 217. This is not as sharp a peak or as high intensity of that of the complex of the invention. Holding the emission at 488 nm gives an excitation peak at 190 nm as with the Pt(sal).sub.2 complex.

[0354] FIG. 8 also shows that for Pt(acac).sub.2 in siloxane with an excitation of 190 nm the main peak again occurs at 490 nm with a higher intensity of 704. However, the emission spectrum also shows a peak at 419 nm with intensity 541—this also with the Pt(sal)2 complex in this solvent. When the emission is held at 405 nm the excitation shows a peak at 328 nm, however it was not recorded below 250 nm so a peak at 190 nm was not seen. With an excitation at 328 nm, a broad emission peak is observed between 370 and 410 nm with an intensity of approx. 210.

[0355] Solubility

Example 15

[0356] The solubility of the product of Example 3 was tested in various solvents.

[0357] In each case, 10 mg of the complex was stirred in 1 mL of each solvent at room temperature for three hours. The solvent was then filtered. One hundred fold dilutions of the samples into methoxypropanol were then carried out and Pt content was determined by ICP-AES using a Spectro Ciros Vision ICP-OES. Yttrium was employed as an internal standard at a concentration of 5 ppm.

[0358] The results are shown below.

TABLE-US-00003 Solvent Pt concentration/mg L.sup.−1 Water 42.1 Water:MeCN (1:1) 167 MeCN 588 Acetone:MeCN (1:1) 698 IPA 43.4 Acetone 646 MeCN:DMSO (80:20) 1220 Toluene 346 Chloroform 3260 MIBK 369 EtOH 103

[0359] Catalytic Testing

Example 16

[0360] The product of Example 3 was tested for catalytic activity.

[0361] 5 mg of the product was dissolved in 1 mL dichloromethane to provide a solution (‘Solution A’).

[0362] The following ingredients were added to a UV-grade plastic cuvette: [0363] vinyl terminated polydimethyl siloxane 100 cSt DMS V21 (2g); [0364] (45-55% methylhydrosiloxane)dimethylsiloxane copolymer 10-15 cSt HMS-501 (0.108 mL); [0365] Solution A (25 μL).

[0366] The contents of the cuvette were stirred briefly with a spatula to ensure thorough mixing and a 10 mm magnetic flea was added, before sealing with parafilm.

[0367] The cuvette was placed in a UV-lamp box. The positioning of samples in the box was kept the same throughout testing (154 mm from ground to top of cuvette; 114 mm between end of housing and front of cuvette).

[0368] A 300 W ozone-free Xenon lamp was used (visible to 300 nm). A water-cooled filter removes some of the visible spectrum.

[0369] The stirrer speed was set to the 12 o'clock position and the lamp was switched on for 60 seconds only. The time taken from the switching on of the lamp to the stirrer no longer being able to complete a turn was noted as a measure of activity.

[0370] Results are provided in the Table below. ‘Irradiated’ indicates samples exposed to the 60 s UV radiation. ‘Dark’ indicates samples left in darkness without any irradiation.

TABLE-US-00004 Sample Time until gelling/s Observations Example 3 (irradiated) 165 Bubbling observed and colour faded from strong yellow to very pale Example 3 (dark) 13,500

[0371] It can be seen that the composition containing the catalyst of Example 3 cured very quickly when exposed to UV light and only showed gelling after a very prolonged period when kept in the dark.

Example 17

[0372] The product of Example 7 and Product 6A from Example 6 were tested for catalytic activity in a similar manner as Example 16, except that 11 mg of the product was dissolved in 1 mL dichloromethane in the initial step. All other aspects of the test were the same as Example 16. The results reflect gelling time after the 60 s UV irradiation.

[0373] The results were as follows:

TABLE-US-00005 Sample Time until gelling/s Product 6A 720 Product of Example 7 208

Example 18

[0374] This Example compares the catalytic activity of the Pt(II) complex of the invention made in Example 3 with that of a well-known complex, Pt(acac).sub.2.

[0375] The testing was done as in Example 16, except that in the initial step the following four solutions were prepared:

TABLE-US-00006 Solu- Amount of Amount of Conc/ tion Complex Solvent complex/mg solvent/mL mM B Pt(sal).sub.2 (Example 1) DCM 45 9 14.4 C Pt(acac).sub.2 DCM 40.2 9 14.4 D Pt(sal).sub.2 (Example 1) Toluene 15.5 20 1.77 E Pt(acac).sub.2 Toluene 14 20 1.77

[0376] Different amounts of the respective solutions, as shown in the Tables below, were added to the cuvette but all other aspects of the test were the same as Example 16. The results are also shown in the Tables below.

TABLE-US-00007 Amount of solution/μL Solution Gelling time/s 25 B 857 C 1234 50 B 489 C 719 75 B 299 C 506 100 B 356 C 535

TABLE-US-00008 Amount of solution/μL Solution Gelling time/s 25 D 1263 E 3544 50 D 627 E 1350 75 D 415 E 938 100 D 319 E 793 200 D 231 E 551 360 D 126 E 486

[0377] The results show that the inventive complex is much more catalytically active than Pt(acac).sub.2. The effect is more pronounced in toluene solvent than DCM.

Example 19

[0378] The product of Example 10 was tested for catalytic activity in a similar manner as Example 16, except that 14 mg of the product was dissolved in 1 mL dichloromethane in the initial step. All other aspects of the test were the same as Example 16. The results reflect gelling time after the 60 s UV irradiation. The time until gelling was 23 minutes and 15 seconds.

[0379] Thermal Stability

Example 20

[0380] Thermogravimetric analysis of the product of Example 3 was carried out, and the results are shown in FIG. 9. The results show that the product is stable up to 200° C. (which is the boiling point for salicylaldehyde). Above this temperature the ligand is lost, leaving behind the platinum metal.