FIELD OF THE INVENTION

The present invention relates to new phosphine compounds, more particularly to substituted triphenylphosphines, a process for obtaining the same and their use as ligands in the catalysis field and other several applications.

BACKGROUND OF THE INVENTION

Phosphines are among the most widely ligands used in homogeneous catalysis. These trivalent phosphorus compounds stand out from other metal ligands inter alia because they are, in principle, easily modified by a well-established chemistry. In this regard, the stereo electronic tuning of the ligands is key in order to optimize a given catalyzed transformation. It is known that arylphosphines are more stable against oxidation than alkylphosphines. Likewise, arylphosphines are weak sigma electron donors compared to the alkylphosphines. Further, the presence of electron-withdrawing (electronegative) groups such as trifluoromethyl on the aryl rings of a phosphine decreases the sigma-donating capacity of the ligand, and at the same time, provides an increase in backbonding ability, decreasing as a whole the electron density on the phosphorus atom. This fact may facilitate coordination and/or dissociation of the ligand to metal center, depending on the rest of ligands presented in the area of the metal, changing the rate of one or more of the various steps comprised in a catalytic cycle. Therefore, phosphines can exhibit a range of sigma donor and pi-acceptor capabilities, and the electronic properties of a metal center in a coordination complex of a metal with phosphines can be tuned by the substitution of electronically different phosphines.

Further, the incorporation of sulfonated groups into the structure of the ligands allows the development of biphasic catalytic reactions. The use of sulfonated phosphine metal complexes as catalysts in such reactions allow the separation of the reaction products from the catalyst and then reuse the latter, as in the case of heterogeneous catalysts, without losing the characteristic selectivity of the molecular or ionic catalysts in homogeneous phase. Biphasic processes require that the catalyst is soluble in only one phase, while the substrates and products remain in the other. In this sense, sulfonated groups allow to retain the catalyst preferentially in polar phases, such as water or ionic liquids, while substrates and products remain in a non-polar phase and are separated at the end of the reaction, for example by simple decantation. Although the system formed by water-organic solvent is undoubtedly the most studied solvent combination in catalytic reactions with sulfonated phosphines, also applications of this type of ligands in biphasic catalysis, such as semipolar solvent-organic solvent, ionic liquid-organic solvent or ionic liquid-supercritical C0 ₂ among others, have also been disclosed.

Sulfonated phosphines, particularly triphenylphosphine monosulfonate (TPPMS) and triphenylphosphine trisulfonate (TPPTS), have been used as ligands in many catalytic reactions such as hydroformylation, carbon-carbon cross-coupling, selective hydro genation, Heck reaction and telomerisation. The most important industrial process that uses this type of ligands, namely water-soluble organometallic complexes comprising TPPTS as ligand, is the Ruhrchemie - Rhone Poulenc process for hydroformylation of propene and to a lesser scale of 1-butene. Monosulfonated phosphines, such as TPPMS are used in the preparation of different fine chemicals. For instance, TPPMS is used by Kuraray for the preparation of nonadienol.

However, the sulfonation reaction commonly used in the preparation of sulfonated triphenylphosphines requires a strict control of the working conditions since the overexposure of the phosphine to fuming sulfuric acid (oleum) may give place to undesired polysulfonation and oxidation products.

To the best of the knowledge of the inventors, there are only two references related to triphenylphosphines which have fluorinated and sulfonated groups on the phenyl rings.

Fell and colleagues were able to introduce sulfonic groups in aromatic rings slightly deactivated by the presence of fluorine atoms as depicted in figure 1 (Fell, B. and Papadogianakis, G. J. Prakt. Chem., 1994, 336, 591). However, long reaction times were required and it was not possible to obtain the pure ligands. The mixture of the di- and trisulfonated products was used in the biphasic hydro formylation of n-hexene catalyzed by rhodium, giving better regioselectivity towards linear aldehyde than their n -fluorinated sulfonated counterparts.

Figure 1

In 2006, Gulyas and colleagues published the synthesis and catalytic application of the ligand depicted in figure 2 (Gulyas, H.; Bacsik, Z.; Szollosy, A.; Bakos, J. Adv. Synth. Catal, 2006, 348, 1306). This ligand is the only example described of a sulfonated phosphine containing electro-withdrawing CF ₃ groups. However, the presence of an electro-donating methoxy group in the sulfonated ring, which is essential in the synthetic strategy used by the authors, reduces the acidic properties of the phosphine. This phosphine is insoluble in water but soluble in ionic liquids, allowing its use in non- water based liquid-liquid biphasic catalysis.

Figure 2

It is therefore necessary to solve the problems associated with the phosphines belonging to the above state of the art and provide new phosphine ligands which show a strong π- acid character and simultaneously they are able to be used under liquid-liquid biphasic conditions both water-based and non aqueous in catalytic process. Advantageously, said ligands must be also readily synthesized in pure form. SUMMARY OF THE INVENTION

The present invention provides substituted triphenylphosphines containing at least one phenyl ring substituted with a sulfonic group and at least another phenyl ring with one or more trifluoromethyl groups without any electro-donating groups. These new phosphines show a high electro-withdrawing effect, which may be fine-tuned by varying the phenyl ring substitution pattern and this favors their use as ligands in metal catalysed reactions. Likewise, the phosphines disclosed herein have a good water solubility and therefore they are suitable for the development of catalytic reactions in water-based biphasic systems. Furthermore, the stability against the oxidation of these phosphines is remarkable in comparison to other sulfonated phosphines reported in the state of the art such as TPPMS or TPPDS. Moreover, the phosphines of the invention are obtained in good quality and yield as it is described latter in this specification. There fore , in a first asp e ct, the pre s ent invention i s directe d to nove l triphenylphosphines of Formula (I) (also referred to as the compounds or phosphines of the invention)

Formula (I)

wherein

M is a proton or a monovalent or divalent cation,

n is an integer selected from 1 and 2,

p takes a value selected from ½, 1 and 2,

Ri is selected from H, Ci-Cis alkyl, CF ₃ and S0 ₃ ^~ ,

Pvi i , R12 and R 3 are independently selected from H and Ci-Cis alkyl, the proviso that

if Ri is S0 ₃ ^" , then

the product of n and p is equal to 2,

R ₂ , R3 and R ₅ are independently selected from H and Ci-Cis alkyl, R4 IS H,

R5-R10 are independently selected from H, Ci-Cis alkyl and CF ₃ , at least one of R5-R10 being CF ₃ ;

if Ri is not S0 ₃ ^" , then

the product of n and p is equal to 1,

R1-R10 are independently selected from H, Ci-Cis alkyl and CF ₃ , at least one of the groups R1-R10 being CF ₃ .

In another aspect, the present invention is directed to a process for obtaining a tryphenylphosphine of Formula (I), which comprises the reaction between a compound of Formula (II)

Formula (II) wherein

R1-R10 are independently selected from H, Ci-Cis alkyl and CF ₃ , at least the groups R1-R10 being CF ₃ ,

R11 , Ri ₂ and Ri ₃ are independently selected from H and Ci-Cis alkyl,

and a sulfonation reagent in presence of a Lewis acid. In another aspect, the present invention is directed to novel triphenylphosphines of Formula (I) obtainable by the above mentioned process. The use of a Lewis acid as an additive allows the direct sulfonation of trifluoromethylated triphenylphosphines since it is able to interact with the lone electron pair of the phosphine's phosphorous atom, preventing its oxidation.

Other aspects of the invention are the uses of the triphenylphosphines of Formula (I). In this regard, the phosphines of the invention are particularly useful as metal ligands in different organic transformations catalysed or promoted by metal complexes, preferably in biphasic systems, most preferably in water-based biphasic systems, but also in biphasic systems were the polar phase is an ionic liquid or other polar media. The catalytic reactions can be also carried out in homogenous phase, provided that a polar solvent is used in which the catalyst and the reagents are soluble. In this case, the catalyst can be recovered at the end of the reaction by adding water and extracting the catalyst into the aqueous phase. The phosphines of Formula (I) are also useful in the stabilization of metallic nanoparticles, which can be employed in several applications such as catalysis, therapy, medical diagnosis, etc.

These and further aspects of the invention are defined in the claims. DETAILED DESCRIPTION OF THE INVENTION

In the above definition of compounds of Formula (I) the following terms have the meaning indicated:

C1-C18 alkyl refers to a straight or branched hydrocarbon chain radical consisting of carbon and hydrogen atoms, containing no unsaturation, having one to eighteen carbon atoms, and which is attached to the rest of the molecule by a single bond, e. g., methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, n-pentyl, etc. In particular embodiments of the present invention, alkyl radicals are selected from long-chain alkyl groups (e.g. alkyl groups having seven to eighteen carbon atoms) or branched alkyl groups (e.g. i-propyl, i-butyl, s-butyl, t-butyl, etc.). In other particular embodiments, alkyl radicals are selected from short-chain alkyl groups (e.g. alkyl groups having one to six (i.e. 1, 2, 3, 4, 5 or 6) carbon atoms such as methyl, ethyl and n-propyl), preferably straight. In an even more preferred embodiment, short-chain alkyl groups have one to four carbon atoms. As will be readily appreciated by one skilled in the art, the phosphines of the invention may also contain alkyl groups having different structures (for instance, long- chain and short-chain alkyl groups together, branched and short-chain alkyl groups together, etc.).

The cation in Formula (I) is selected in such a way that the general charge of Formula (I) is neutral. Therefore, the invention also provides salts of compounds of Formula (I). For instance, salts of compounds provided herein are synthesized from the parent compound which contains an acidic moiety by conventional chemical methods. Generally, such salts are, for example, prepared by reacting the free sulfonic acid group or groups with a stoichiometric amount of the appropriate base in water or in an organic solvent or in a mixture of the same. Examples of the addition salts include inorganic salts wherein the cation is selected from monovalent or divalent cations selected from the group comprising of alkaline elements, alkaline earth elements, Cu ⁺ , Ag ⁺ , Au ⁺ and cations of the formula R14R15R16 RnN ⁺ wherein R14, R15, Ri ₆ and Ri ₇ are selected from the group comprising hydrogen and C ₁ -C4 alkyl groups which are optionally substituted, for example by one or more hydroxyl groups. More preferably the cations are select from the group comprising, sodium, potassium, calcium, ammonium cations such as, those derived from, for example, ethylenediamine, ethanolamine, Ν,Ν-dialkylenethanolamine, triethanolamine and basic aminoacids salts. Preferred salts of the compounds of the invention are sodium salts.

The compounds of the invention may be in amorphous or crystalline. The crystalline compounds either may be in the form of free compounds or in the form of solvates thereof (e.g. hydrates, alcoholates, particularly methanolates) and it is intended that both forms are within the scope of the present invention. Methods of solvation are generally known within the art. The compounds of the invention may present different polymorphic forms, and it is intended that the invention encompasses all such forms. Unless otherwise stated, the compounds of the invention are also meant to include compounds which differ only in the presence of one or more isotopically enriched atoms. For example, compounds having the present structures except for the replacement of hydrogen by deuterium or tritium, or the replacement of a carbon by a ¹³ C- or ¹⁴ C-enriched carbon or ¹⁵ N-enriched nitrogen are within the scope of this invention.

As introduced above, the present invention is directed to novel triphenylphosphines of Formula (I).

Depending on the sulfonation degree, the phosphines of Formula (I) can be divided into two groups:

a) Trifluoromethylated disulfonated phosphines of Formula (la)

Formula (la)

wherein

M is a proton or a monovalent or divalent cation,

n is an integer selected from 1 and 2,

p takes a value selected from 1 and 2,

R ₂ , R ₃ , R-5, Ri i, Ri2 and Ri ₃ are independently selected from H and Ci-Cis alkyl, R5-R10 are independently selected from H, Ci-Cis alkyl and CF ₃ , at least one of Re-Rio being CF ₃ . In a particular embodiment of Formula (la), R ₂ , R3, R5, Rn, Ri ₂ and R13 are H and R6- R10 are independently selected from H and CF ₃ , at least one of R5-R10 being CF ₃ .

Preferred phosphines of Formula (la) are those depicted below:

b) Trifluorometh lated monosulfonated phosphines of Formula (lb)

Formula (lb)

wherein

M is a proton or a monovalent or divalent cation,

n is an integer selected from 1 and 2,

p takes a value selected from ½ and 1 ,

Rn, Ri ₂ and R13 are independently selected from H and Ci-Cis alkyl,

R1-R10 are independently selected from H, Ci-Cis alkyl and CF ₃ , at least one of the groups R1-R10 being CF ₃ .

In a particular embodiment of Formula (lb), Rn, Ri ₂ and R13 are H and R1-R10 are independently selected from H and CF ₃ , at least one of the groups R1-R10 being CF ₃ . In another particular embodiment of Formula (lb), Rn, R12 and R13 are independently selected from H and Ci-Cis alkyl, at least one of the groups Rn-Rn being Ci-Cis alkyl, and R1-R10 are independently selected from H and CF ₃ , at least one of the groups R1-R10 being CF ₃ . In this last embodiment, preferably R12 is Ci-Cis alkyl (more preferably methyl).

Preferred phosphines of Formula (lb) are those depicted below:

10

Phosphines of Formula (lb) may be divided in turn into another two groups: those having two trifluoromethylated rings (such as phosphines 4, 5, 6 and 10) and those having only one trifluoromethylated ring (such as phosphines 7, 8 and 9).

In another particular embodiment, M is selected from a proton, sodium, potassium, calcium, an ammonium cation such as, those derived from, for example, ethylenediamine, ethanolamine, Ν,Ν-dialkylenethanolamine, triethanolamine and basic aminoacids salts. Preferred salts of the compounds of the invention are sodium salts.

The skilled person will select the alkyl radicals forming part of the phosphines of the invention depending on the application desired. For instance, when bulky phosphines are sought, the alkyl radicals mentioned in any of the positions R1-R13 of the formulae described herein are preferably selected from long-chain alkyl groups (e.g. alkyl groups having seven to eighteen carbon atoms) or branched alkyl groups (e.g. i-propyl, i-butyl, s-butyl, t-butyl, etc.). By contrast, when a low steric hindrance is sought, the alkyl radicals are preferably selected from short-chain alkyl groups (e.g. alkyl groups having one to six carbon atoms such as methyl, ethyl and n-propyl), more preferably straight. In an even more preferred embodiment, short-chain alkyl groups have one to four carbon atoms. As will be readily appreciated by one skilled in the art, the phosphines of the invention may also contain alkyl groups having different structures (for instance, long- chain and short-chain alkyl groups together, branched and short-chain alkyl groups together, etc.).

The present invention is also directed in a particular embodiment to triphenylphosphines of formulae (I), (la) or (lb) wherein one or more of the Ci-Cis alkyl radicals defined in any of the positions R1-R13 are independently selected from a Ci-C ₆ alkyl radical. In this embodiment, a preferred alkyl radical is methyl.

In additional preferred embodiments, the preferences described above for the different substituents are combined. The present invention is also directed to such combinations of preferred substitutions in the Formula (I) above.

Due to the substitution on the phenyl rings with CF ₃ and S0 ₃ M groups these new phosphines show a high π-acid character. In this regard, it should be noted that the electron-withdrawing capacity of a CF ₃ group is much higher than that of a F atom, as is shown by the fact that the phenyl rings in P(/?-C ₆ H ₄ F) ₃ are reactive in electrophilic substitution with oleum, while phosphines with three phenyl rings substituted with CF ₃ are not. It is known that a strong π-acid character is especially favorable for a number of catalytic processes. In particular, in the hydro formylation of 1-alkenes higher rates and higher selectivities towards the linear aldehyde have been reported for some of the phosphines of Formula (II) when compared with triphenylphosphine. Further, these phosphines present in general good solubility in water. Particularly, phosphines of Formula (la), i.e. disulfonated phosphines (such as phosphines 1, 2 or 3) and phosphines of Formula (lb) having only one ring trifluromethylated (such as phosphines 7, 8 and 9) are freely soluble in water (typically equal or above 3 g/100 mL), whilst phosphines of Formula (lb) having two rings trifluoromethylated (such as phosphines 4, 5, 6 and 10) are moderately soluble in water (typically about 1 g/100 mL, for instance between 0.2 and 1.2 g/100 mL).

Moreover, because the low basicity of these phosphines, they are significantly more robust against aerial or other type of oxidation than the corresponding phosphines without trifluoromethyl substituents. For instance, while 5 · 10 ^"2 mM aqueous solution of sulfonated phosphines NaTPPMS and Na ₂ TPPDS readily oxidize in the air at room temperature (about 5% in 16 h), the same solutions of several phosphines of the invention are completely stable for at least a period of 16 h. This stability could be important in catalytic processes and particularly in those involving recycling of the catalytic species.

Several synthetic processes have been tried in order to prepare the new phosphines of Formula (I). Common sulfonation conditions by means of a direct electrophilic aromatic substitution did not yield the desired sulfonated products producing only a mixture of the starting materials and the phosphine oxide whereas other synthetic routes did not give place to any reaction. Finally, the synthesis of the phosphines of Formula (I) was conveniently achieved by protecting the phosphorus atom against oxidation which allows the use of severe sulfonation conditions. More specifically, the sulfonation over trifluoromethylated triphenylphosphines in presence of a Lewis acid as protecting agent avoids the oxidation of the phosphorus atom. This process of sulfonation is disclosed in US 5,451,698. A Lewis acid is a molecular entity (and the corresponding chemical species) that is an electron-pair acceptor and therefore able to react with a Lewis base such as the phosphorus atom in phosphines to form a Lewis adduct, by sharing the electron pair furnished by the Lewis base. Examples of Lewis acids include: boric acid, halides of boron and other halides (such as of aluminium, phosphorus, antimony, arsenic, iron, zinc, and tin). The Lewis acid used in the process for obtaining the phosphines of the invention is preferably a boron compound. Most preferably, said Lewis acid is boric acid B(OH) ₃ which is an inexpensive material, commercially available. The amount of Lewis acid preferably ranges from about 2 to about 10 equivalents for each equivalent of phosphine to be sulfonated, most preferably from about 4 to about 8 equivalents. In general, about 4 equivalents of Lewis acid are suitable for the reaction occurs. Conveniently, a solution of the Lewis acid is prepared by dissolving the acid in concentrated sulfuric acid, such as H ₂ SO ₄ 95 wt. % followed by deoxygenation, for example, by nitrogen bubbling. Next, the starting phosphine of Formula (II) is dissolved portion- wise into the above solution. This step is carried out preferably at a temperature of about 0 °C which may be maintained during the addition of the sulfonation reagent. Sulfonation reagents include: fuming sulfuric acid, stabilized S0 ₃ , such as amine- stabilized S0 ₃ , pyridine-stabilized S0 ₃ , trimethylsilyl sulfonyl chloride, commercially available S0 ₃ and mixtures thereof. In a preferred embodiment, said sulfonation reagent is oleum or fuming sulfuric acid (H ₂ S0 ₄ /S0 ₃ ). Concentrations of oleum are usually either expressed in terms of % S0 ₃ by weight (called % oleum) or as % H ₂ SO ₄ (the amount obtained when H ₂ 0 is added). Common concentrations and suitable for the present invention are from 20% to 65%> oleum such as 20%> oleum (104.5%) H ₂ SO ₄ ), 40% oleum (109% H ₂ S0 ₄ ) and 65% oleum (1 14.6% H ₂ S0 ₄ ). The most preferred concentration is 65% oleum. Further, the oleum is typically added in an amount from about 20 to about 120 equivalents of S0 ₃ for each equivalent of phosphine to be sulfonated, for example about 20, about 30, about 40, about 50, about 60, about 70, about 80, about 90, about 100, about 110 or about 120 equivalents. During the addition of the sulfonation reagent temperature is preferably kept low, for example at about 0 °C, while it is vigorously stirred to provide an uniform mixture.

The sulfonation typically proceeds at room temperature. It has shown that temperatures above about 25 °C may yield phosphorus oxidation products. The progress of the reaction may be conveniently monitored by ³¹ P{ ¹ H} NMR, which makes possible the easy differentiation of the trivalent and pentavalent phosphorus species in the crude reaction mixture. ³¹ P{ ¹ H} NMR experiments can be carried out in accordance with established literature. For example, a small aliquot is taken from the mixture and then it is dissolved in a suitable solvent, such as a mixture of methanol:D ₂ 0 (0.9 ml:0.1 ml), in such a way that all species are dissolved. The spectra may be conveniently calibrated using 85% H ₃ PO ₄ . As soon as the desired phosphine is obtained, an usual work-up affords the same in good yield and purity. The rate of sulfonation depends on several factors such as reaction times or the steric hindrance of the starting phosphine. In this respect, triphenylphosphines substituted with CF ₃ groups in para positions provides shorter reaction times (even only 1 h) whereas the reactivity of phosphines substituted with orto-trifluoromethylphenyl groups is lower. In any case, the process disclosed herein allows a prompt access to phosphines of Formula (I). Briefly, from an experimental standpoint, the process for obtaining a tryphenylphosphine of Formula (I) comprises:

• dissolving the Lewis acid into concentrated sulfuric acid;

• dissolving the starting phosphine of Formula (II) into the acid solution formed in the previous step, preferably portion-wise and at about 0 °C;

· adding the sulfonation reagent, preferably drop-wise and at about 0 °C;

• quenching the reaction by slowly adding the reaction mixture to water, which has preferably been degased; and

• when it is desired to obtain the compound in the form of a salt, neutralizing the mixture with an appropriate base.

The starting phosphines of Formula (II) may be easily prepared following well-known procedures in the state of the art [e.g. Miller, G.R.; Yankowsky, A.W.; Grim, S.O., J. Chem. Phys., 1969, 51, 3185; Adams, D. J.; Bennett, J.A.; Cole-Hamilton, D.J.; Hope, E.G.; Hopewell, J.; Kight, J.; Pogorzelec, P.; Stuart, A.M., Dalton Trans., 2005, 24, 3862; Zhmurova, I. N.; Kirsanov, A. V., Zhurnal Obshchei Khimii, 1966, 7, 1248]. These procedures may firstly comprise the reaction between a trifluoromethylated aryl halide with a metal (for instance, Li or Mg) or an organometallic reagent (for instance, an organo lithium or organomagnesium reagent) to form an organametallic trifluoromethylated aryl (for instance, ArMgX or ArLi). Subsequently, the intermediate formed reacts with a chlorodiarylphosphme (stoichiometric relationship 1 : 1) or a dichloroarylphosphine (stoichiometric relationship 2: 1). In the latter case, the sequential addition of two different arylorganometallic compounds may give place to a phosphine of Formula (II) comprising three different aryl rings. Said sequential addition preferably comprises the isolation of the chlorodiarylphosphme obtained from the first reaction, before adding the second arylorganometallic compound. Chlorodiarylphosphines and dichlorodiarylphosphines are commercial products or can be prepared following well known procedures [e.g. Liddle, S.T.; Izod, K., Organometallics, 2004, 23, 5550; Whitaker, CM.; Kott, K.L.; McMahon, R.J., Journal of Organic Chemistry, 1995, 60, 3499].

The phosphines of the present invention may show great application as ligands in various catalyzed or promoted chemical transformations by metal complexes such as hydro genation; hydro silylation; carbon-carbon and carbon-heteroatom double bond hydroboration; alkene hydro amination; alkene and diene telomerization, oligomerization and polymerization; alkene and diene isomerization, hydro cyanation, hydro formylation and hydrocarboxylation; aryl and vinyl halide and alcohol carbonylation; hydratation reactions, notably of nitriles, alkynes and alkenes; carbon- carbon and carbon-heteroatom cross-coupling reactions. As described, these ligands are easy to synthesize and also to be modified depending on the number and position of the Ci-Cis alkyl, CF ₃ and S0 ₃ ^~ groups to enhance the catalytic activity of metals such as rhodium or palladium. This variation both in electronic and steric properties is required in order to achieve the most suitable ligand for each process. Further, the resistance to oxidation of the phosphines of the invention allows their use under oxidant conditions and reactions.

The ligands of the invention may be used in homogenous catalysis, provided that a polar solvent is used in which the catalyst and the reagents are soluble. In this case, the catalyst can be recovered at the end of the reaction by adding water and extracting the catalyst into the aqueous phase. The water-soluble ligands of the invention are particularly advantageous when used in biphasic catalytic systems, improving the efficiency of product isolation and catalyst recovery which is achieved by simply removing the aqueous phase from the organic phase. The ligands are also suitable for any other biphasic catalytic system containing a polar phase, such as an ionic liquid.

Likewise, the phosphines of the present invention may also be used in the preparation and stabilization of metal nanoparticles or clusters in polar media, which have different applications such as catalysis, therapy or medical diagnosis.

The use of metal clusters in conventional homogenous processes has been widely studied because they are considered to have properties intermediate between homogenous and heterogeneous catalysts. As a cluster consists of several metal atoms, activation of an organic substrate may take place at more than one metal atom and this can have a profound effect on the activity. The synthesis of water-soluble clusters may be achieved by the replacement of one or more labile ligands with the water-soluble phosphine ligand of the invention in a suitable solvent. Protective agents are imperative for the stabilization of nanostructured metals and for prevention of their coagulation. In this respect, phosphines act as protective shields on the metallic surface and thus the nanometallic cores are separated from each other. For example, the metal nanoparticles formed by the phosphines of the invention may be used as diagnostic or therapeutic radiopharmaceuticals.

The invention will be further illustrated by means of examples. These should be interpreted merely as illustrative of the invention. EXAMPLES

1. Preparation of the trifluoromethylated phosphines of Formula (II) precursors of phosphines 1-10

The starting material is a phenyl halide containing at least one trifluoromethyl group in its structure:

wherein

X is F, CI or Br,

RrRio are independently selected from H or CF ₃ , at least one of the groups Rio being CF ₃ ,

When Re, Rio or both of them are CF ₃ , the phenyl halide (22.4 mmol) was dissolved in diethyl ether (30 ml) and cooled down to 0°C n-BuLi (2.5 M in hexane, 22.3 mmol) was added dropwise and the reaction mixture was stirred for one hour. A solution of chloro dip henylp ho sp hine ( 1 9 .9 mmo l) [ for p ho sp hine s 3 and 9 ] or dichlorophenylphosphine (10.3 mmol) [for phosphine 6] in Et ₂ 0 (10 ml) was added to the lithium derivative. After the addition, the reaction mixture was allowed to warm up slowly to room temperature and stirred for 3 hours.

When Re and Rio are not CF ₃ , the phenyl halide (34.1 mmol) was dissolved in Et ₂ 0 (50 ml) and added into a magnesium (51.0 mmol) suspension in Et ₂ 0 (50 ml) at 0°C. The mixture was refluxed during 2 hours and the magnesium excess was filtered via canula. A solution of chlorodiphenylphosphine (31.0 mmol) [for phosphines 1, 2, 7 and 8], dichlorophenylphosphine (15.9 mmol) [for phosphines 4 and 5] or dichloro-/?- tolylphosphine (15.9 mmol) [for phosphine 10] in Et ₂ 0 (10ml) was slowly added to the Grignard solution and the mixture was refluxed for 2 hours. The general work up involved the addition of a hydrochloric acid solution (10%). After the phase separation, the organic phase was washed with water, dried over MgS0 ₄ , and the solvent was removed in vacuo. The products were purified by gel chromatography or with a reduced pressure distillation.

Characterization data of phosphine of formula (II) precursor of phosphine 10 are depicted below:

Chemical Formula: C ₂ iHi5F ₆ P

Molecular Weight: 412.31

NMR

1H NMR: 400.13 MHz, CDC1 ₃ , δ (ppm): 7.59 (bd, 4H, Hc ₃ {C ₆ H ₄ CF ₃ } , ³ J _HH = 7.9Hz); 7.40 (bt, 4H, H _C2 {C ₆ H4CF3} , ³ J _HH = ³ ½» = 7.9Hz); 7.26-7.20 (m, 4H, H _C2 {C6H ₄ CH ₃ } - Hc3 {C ₆ H ₄ CH3}); 2.39 (s, 3H, ¾∞).

³¹ P{1H} NMR: 145.78 MHz, CDC1 ₃ , δ (ppm): -6.07 (s).

¹⁹ F{1H} NMR: 235.39 MHz, CDC1 ₃ , δ (ppm): -62.83 (s).

HRMS: ESI m/z

[M+H ⁺ ] = 413.0880 exp.; 413.0888 calculated for C ₂ iHi ₅ F ₆ P.

2. Preparation of trifluoromethylated sulfonated phosphines of Formula (I)

Phosphines 1-10 wherein M is Na ⁺ were synthesized according to the following general procedure:

Boric acid was dissolved into concentrated sulfuric acid (95%> w/w) and N ₂ was bubbling for 15 min in order to prevent the presence of oxygen in the reaction mixture. Under N ₂ atmosphere, the starting phosphines of Formula II were dissolved into the acid solution portion-wise at 0 °C. Once the phosphines were completely dissolved, fuming sulfuric acid comprising SO ₃ 65% was added drop-wise for 1 h keeping the reaction temperature at 0°C.

The reaction was allowed to reach room temperature and aliquots were taken at different times and analyzed by ³¹ P{ ¹ H} NMR to monitor the progress of the same. Once obtained the desired sulfonation degree, the reaction was quenched pouring the reaction mixture into frozen and deoxygenated water at 0°C (50% w/w). Then, it was neutralized with a solution of deoxygenated NaOH keeping the temperature below 10 °C. Water was evaporated affording a mixture of inorganic salts and phosphines which were extracted with methanol. Then, the methanol was evaporated and the product was washed with CH ₂ CI ₂ to remove possible unreacted starting material or by-products. Recrystallization, from water in the case of monosulfonated phosphines (formula lb) and from methanol in the case of disulfonated phosphines (formula la), afforded the desired sulfonated phosphine as a white solid. The amounts of the reagents (expressed as equivalents for each equivalent of starting phosphine), reaction times and yields are showed below.

SOs 60

(eg.)

Time

(h)

Yield

63

(%)

Sodium 3,3'-((p-trifluoromethylphenyl)phosphinediyl)dibenzenesulfon ate [l-(Na)]

Chemical Formula: C19H12F3O6PS2 Na ₂

Molecular Weight: 534,37

Freely soluble in water

NMR

1H NMR: 400.13 MHz, CD ₃ OD, δ (ppm): 7.92 (dtd, 2H, H _C2 {C ₆ H ₄ S0 ₃ Na}, ³ J _HP = 8.3Hz - ⁴ J _HH = 1.7Hz - ⁵ J _HH = 0.5Hz); 7.72 (bd, 2H, H _C 6 {C6H ₄ S03Na}, ³ J _HH = 7.7Hz); 7.66 (bd, 2H, Hc3 {C ₆ H ₄ CF ₃ }, ³ J _HH = 8.0Hz); 7.47 (m, 4H, H _C2 {C ₆ H ₄ CF3} + Hc ₅ {C ₆ H ₄ S03Na}); 7.37 (bt, 2H, H _C4 {C ₆ H ₄ S0 ₃ Na}, ³ J _HH = ³ JHP = 7.7Hz).

1 ³ C{1H} NMR: 100.61 MHz, CD ₃ OD, δ (ppm): 147.02 (d, Ci {C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 7.8Hz); 143.58 (d, Ci {C ₆ H ₄ CF ₃ }, 'JCP = 13.9Hz); 137.71 (d, C ₃ {C ₆ H ₄ S0 ₃ Na}, ^CP = 13.4Hz); 136.46 (d, C ₄ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 17.2Hz); 134.98 (d, C ₂ {C ₆ H ₄ CF ₃ }, ² J _C p = 19.6Hz); 132.40 (d, C ₂ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 25.3Hz); 131.88 (q, C ₄ {C ₆ H ₄ CF ₃ }, ² J _CF = 32.4Hz); 130.05 (d, C ₅ {C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 6.1Hz); 128.14 (s, C ₆ {C ₆ H ₄ S0 ₃ Na}); 126.43 (m, C ₃ {C ₆ H ₄ CF ₃ }); 125.55 (q, C{CF ₃ }, ^CF = 271.5Hz).

3 ¹ P{1H} NMR: 161.98 MHz, CD ₃ OD, δ (ppm): -5.09 (s).

1 ⁹ F{1H} NMR: 376.50 MHz, CD ₃ OD, δ (ppm): -62.07 (s). HRMS: ESI m/z

[M-2Na ⁺ ]/2 = 243.9884 exp.; 243.9888 calculated for Ci ₉ Hi ₂ F ₃ 06PS2.

Sodium 3,3'-((3,5-bis(trifluoromethy])phenyl)phosphinediy])dibenzen esulfonate [2- (Na)]

Chemical Formula: C ₂ oHnF ₆ 06PS ₂ Na ₂

Molecular Weight: 602,37

White solid

Freely soluble in water

NMR

1H NMR: 400.13 MHz, CD ₃ OD, δ (ppm): 7.97-7.90 (m, 5H, H _C 4 {C ₆ H3(CF3) ₂ } - H _c2 - Hc ₆ {C ₆ H ₄ S0 ₃ Na} ); 7.79 (bd, 2H , H _C2 {C ₆ H3(CF ₃ ) ₂ }, ³ J _HP = 6.8Hz); 7.53 (bt, 2H, H _C5 {C ₆ H ₄ S0 ₃ Na} , ³ J _HH = 7.6Hz); 7.40 (tt, 2H, H _C4 {C ₆ H ₄ S0 ₃ Na} , ³ J _HH = ³ JHP = 7.6HZ -

¹³ C{1H} NMR: 90.55 MHz, CD ₃ OD, δ (ppm): 147.32 (d, Ci {C ₆ H ₄ SC>3Na} , J _CP = 8.3Hz); 143.06 (d, d {C ₆ H3(CF ₃ ) ₂ } , ^] J _C p = 19.2Hz); 136.55 (d, C3 {C ₆ H ₄ S0 ₃ Na} , ^] J _CP = 13.1Hz); 136.43 (d, C ₄ {C ₆ H ₄ S0 ₃ Na} , ² J _CP = 16.3Hz); 134.15 (bd, C ₂ {C ₆ H3(CF3) ₂ } , ² J _C p = 20.4Hz); 133.05 (qd, C ₃ {C ₆ H3(CF ₃ ) ₂ } , ² JCF = 33.3Hz - ³ J _CP = 5.8Hz); 132.54 (d, C ₂ {C ₆ H ₄ S0 ₃ Na} , ² JCP = 26.9Hz); 130.39 (d, C ₅ {C ₆ H ₄ S0 ₃ Na} , J _CP = 6.0Hz); 128.65 (s, C ₆ {C ₆ ¾S0 ₃ Na}); 124.59 (q, C {CF ₃ } , 'JCF = 272.4Hz); 123.83 (m,

3 ¹ P{1H} NMR: 145.78 MHz, CD ₃ OD, δ (ppm): -2.88 (s).

1 ⁹ F{1H} NMR: 235.39 MHz, CD ₃ OD, δ (ppm): -62.31 (s).

HRMS: ESI m/z

[M-2Na ⁺ ]/2 = 277.9833 exp.; 277.9825 calculated for C ₂ oHiiF ₆ 0 ₆ PS ₂ .

Sodium 3,3'-((o-trifluoromethy]phenyl)phosphinediy])dibenzenesu]fon ate [3-(Na)] Chemical Formula: C19H12F3O6PS2 Na ₂

Molecular Weight: 534,37 White solid

Freely soluble in water

NMR

1H NMR: 360.13 MHz, CD ₃ OD, δ (ppm): 7.86 (dt, 2H, Hc ₆ {C ₆ H ₄ S03Na}, ³ J _HH = 6.9Hz - ⁴ J _HH = 1 .3Hz); 7.84-7.80 (m, 1H, Hc ₃ {C ₆ H ₄ CF3}); 7.76 (dt, 2H, H _C2 {C ₆ H ₄ S03Na}, ³ J _HP = 6.8Hz - ⁴ J _HH = 1.3Hz); 7.61-7.51 (m, 2H, H _C4 - H _C5 {C ₆ H ₄ CF3}); 7.47 (tdd, 2H, H _C5 {C ₆ H ₄ S03Na}, ³ J _HH = 6.9Hz - ⁴ J _HP = 1.3Hz - ⁵ J _HH = 0.4Hz); 7.31 (tt, 2H, H _C4 {C ₆ H ₄ S03Na}, ³ J _HH = ³ JHP = 6.9Hz - ⁴ J _HH = 1.3Hz); 7.25-7.20 (m, 1H, Hc ₆ {C ₆ H ₄ CF ₃ }).

¹³ C{1H} NMR: 100.61 MHz, CD ₃ OD, δ (ppm): 146.60 (d, Ci {C ₆ H ₄ S0 ₃ Na}, ³ J _CP =

6.5Hz); 138.08 (bd, C ₃ {C ₆ H ₄ S0 ₃ Na}, ^CP = 15.5Hz); 137.49 (d, C ₆ {C ₆ H ₄ CF ₃ }, ² J _C p = 1.9Hz); 136.54 (d, C ₄ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 20.2Hz); 136.34 (d, Ci {C ₆ H ₄ CF ₃ }, 'JCP =

29.2Hz); 135.91 (qd, C ₂ {C ₆ H ₄ CF ₃ }, ² J _CF = 30.1Hz - ² J _CP = 25.9Hz); 133.38 (s,

C ₅ {C ₆ H ₄ CF ₃ }); 131.90 (d, C ₂ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 22.7Hz); 130.99 (s, C ₄ {C ₆ H ₄ CF ₃ });

130.01 (d, C ₅ {C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 6.4Hz); 127.90 (s, C6{C ₆ H ₄ S0 ₃ Na}); 127.70 (m,

C ₃ {C ₆ H ₄ CF ₃ }); 125.78 (q, C{CF ₃ }, 'JCF = 274.6Hz).

3 ¹ P{1H} NMR: 145.78 MHz, CD ₃ OD, δ (ppm): -10.52 (q, ⁴ J _PF = 53.9Hz).

¹⁹ F{1H} NMR: 235.39 MHz, CD ₃ OD, δ (ppm): -55.81 (d, ⁴ J _FP = 53.9Hz).

HRMS: ESI m/z

[M-Na ⁺ ] = 510.9669 exp.; 510.9668 calculated for Ci ₉ Hi ₂ F30 ₆ PS ₂ Na. Sodium 3-(bis(p-trifluoromethylphenyl)phosphino)benzenesulfonate [4-(Na)]

Chemical Formula: C ₂ oHi ₂ Fe0 ₃ PSNa

Molecular Weight: 500,33

White solid

Moderately soluble in water

NMR

1H NMR: 400.13 MHz, CD ₃ OD, δ (ppm): 7.92-7.87 (m, 2H, H _C2 {C ₆ H ₄ S0 ₃ Na} + Hc ₆ {C ₆ H ₄ S0 ₃ Na}); 7.70 (bd, 4H, Hc3 {C ₆ H ₄ CF3}, ³ J _HH = 7.9Hz); 7.53-7.41 (m, 6H, H _C2 {C ₆ H ₄ CF ₃ } + H _C4 {C ₆ H ₄ S0 ₃ Na} + Hc ₅ {C ₆ H ₄ S0 ₃ Na}).

1 ³ C{1H} NMR: 62.90 MHz, CD ₃ OD, δ (ppm): 147.19 (d, Ci {C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 6.9Hz); 142.84 (d, Ci {C ₆ H ₄ CF ₃ }, ^CP = 14.8Hz); 137.08 (d, C ₃ {C ₆ H ₄ S0 ₃ Na}, ^l J _c? = 13.5Hz); 136.77 (d, C ₄ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 21.5Hz); 135.17 (d, C ₂ {C ₆ H ₄ CF ₃ }, ² J _C p = 20.3Hz); 132.30 (d, C ₂ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 21.7Hz); 132.22 (q, C ₄ {C ₆ H ₄ CF ₃ }, ² J _CF = 32.6Hz); 130.14 (d, C ₅ {C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 7.4Hz); 128.40 (s, C6{C ₆ H ₄ S0 ₃ Na}); 126.56 (dq, C ₃ {C ₆ H ₄ CF ₃ }, ³ J _C p = 7.2Hz - ³ J _CF = 3.7Hz); 125.45 (q, C{CF ₃ }, 'JCF = 271.5Hz).

³¹ P{1H} NMR: 161.98 MHz, CD ₃ OD, δ (ppm): -5.98 (s).

1 ⁹ F{1H} NMR: 376.50 MHz, CD ₃ OD, δ (ppm): -62.10 (s).

HRMS: ESI m/z

[M-Na ⁺ ] = 477.0144 exp.; 477.0143 calculated for C ₂₀ Hi ₂ F ₆ O ₃ PS

Sodium 3- bis(3,5-bis(trifluoromethyl)phenyl)phosphino)benzenesulfonat e [5-(Na)]

Chemical Formula: C ₂₂ HioFi ₂ 0 ₃ PSNa Molecular Weight: 636,32

White solid

Moderately soluble in water

NMR

1H NMR: 400.13 MHz, CD ₃ OD, δ (ppm): 8.24 (bm, 2H, Hc ₄ {C ₆ H ₃ (CF ₃ ) ₂ }); 8.16

(dddd, 1H, H _C6 {C ₆ H ₄ S0 ₃ Na}, ³ J _HH = 7.7Hz - ⁴ J _HH = 1.7Hz - ⁴ J _HH = 1.1 Hz - HP

0.8Hz); 8.09 (dtd, 1H, H _C2 {C ₆ H ₄ S0 ₃ Na}, ³ J _HP = 8.7Hz - ⁴ J _HH = 1.7Hz - ⁵ J _HH = 0.6Hz); 8.03 (m, 4H, H _C2 {C ₆ H ₃ (CF ₃ ) ₂ }); 7.77 (tdd, 1H, H _C5 {C ₆ H ₄ S0 ₃ Na}, ³ J _HH = 7.7Hz - ⁴ J _HP

1.4Hz - ⁵ J _HH = 0.6Hz); 7.64 (tdd, 1H, H _C4 {m-C ₆ H ₄ S0 ₃ Na}, ³ J _HH = ½> = 7.7Hz - Ί HH

1.7Hz - J HH 1.1Hz). ¹³ C{1H} NMR: 90.55 MHz, CD ₃ OD, δ (ppm): 147.69 (d, Ci{C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 8.0Hz); 141.19 (d, Ci {C ₆ H ₃ (CF ₃ ) ₂ }, 'JCP = 19.2Hz); 136.68 (d, C ₄ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 19.6Hz); 135.15 (d, C ₃ {C ₆ H ₄ S0 ₃ Na}, ^l ] _c ? = 13.4Hz); 134.50 (bd, C ₂ {C ₆ H ₃ (CF ₃ ) ₂ }, ² J _C p = 20.2Hz); 133.40 (qd, C ₃ {C ₆ H ₃ (CF ₃ ) ₂ }, ² J _CF = 33.7Hz - ³ J _CP = 6.2Hz); 132.56 (d, C ₂ {C ₆ H ₄ S0 ₃ Na}, ² JCP = 24.9Hz); 130.79 (d, C ₅ {C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 6.9Hz); 129.27 (s, C ₆ {C ₆ H ₄ S0 ₃ Na}); 124.56 (sept., C ₄ {C ₆ H ₃ (CF ₃ ) ₂ }, ³ J _CF = 3.5Hz); 124.48 (q, C{CF ₃ },

³¹ P{1H} NMR: 145.78 MHz, CD ₃ OD, δ (ppm): -4.71 (s).

1 ⁹ F{1H} NMR: 235.39 MHz, CD ₃ OD, δ (ppm): -62.34 (s).

HRMS: ESI ^" m/z

[M-Na ⁺ ] = 612.9912 exp.; 612.9902 calculated for C ₂₂ Hi ₀ Fi ₂ O ₃ PS.

Sodium 3- bis(o-trifluoromethylphenyl)phosphino)benzenesulfonate [6-(Na)]

Chemical Formula: C ₂ oHi ₂ F ₆ 0 ₃ PSNa Molecular Weight: 500,33

Moderately soluble in water

NMR

1H NMR: 360.13 MHz, CD ₃ OD, δ (ppm): 7.87 (dt, 1H, H _C6 {C ₆ H ₄ S0 ₃ Na}, ³ J _HH = 7.7Hz - ⁴ J _HH = 1.4Hz); 7.84-7.78 (m, 2H, H _C3 {C ₆ H ₄ CF ₃ }); 7.67 (dt, 1H, H _C2 {C ₆ H ₄ S0 ₃ Na}, ³ J _HP = 7.2Hz - ⁴ J _HH = 1.4Hz); 7.61-7.50 (m, 4H, H _C4 - Hc ₅ {C ₆ H ₄ CF ₃ }); 7.46 (td, 1H, H _C5 {C ₆ H ₄ S0 ₃ Na}, ³ J _HH = 7.7Hz - ⁴ J _HP = 1.2Hz); 7.23 (tt, 1H, H _C4 {C ₆ H ₄ S0 ₃ Na}, ³ J _HH = ³ J _HP = 7.7Hz - ⁴ J _HH = 1.4Hz); 7.11-7.04 (m, 2H, H _C6 {C ₆ H ₄ CF ₃ }).

¹³ C{1H} NMR: 90.56 MHz, CD ₃ OD, δ (ppm): 147.04 (d, Ci{C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 6.1Hz); 137.39 (d, C ₃ {C ₆ H ₄ S0 ₃ Na}, ^l J _c? = 11.6Hz); 137.32 (s, C ₆ {C ₆ H ₄ CF ₃ }); 136.64 (d, C ₄ {C ₆ H ₄ S0 ₃ Na}, ² J _CP =23.5Hz); 136.21 (d, Ci{C ₆ H ₄ CF ₃ }, ^l J _c? = 29.7Hz); 135.40 (qd, C ₂ {C ₆ H ₄ CF ₃ }, ² J _CF = 30.5Hz - ² J _CP = 25.8Hz); 133.21 (s, C ₅ {C ₆ H ₄ CF ₃ }); 132.18 (d, C ₂ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 21.6Hz); 130.81 (s, C ₄ {C ₆ H ₄ CF ₃ }); 129.93 (d, C ₅ {C ₆ H ₄ S0 ₃ Na}, ³ JCP = 7.3Hz); 128.02 (s, C ₆ {C ₆ H ₄ S0 ₃ Na}); 127.91 (m,

C ₃ {C ₆ H ₄ CF ₃ }); 125.70 (q, C{CF ₃ }, 'JCF = 274.5Hz).

³¹ P{1H} NMR: 145.78 MHz, CD ₃ OD, δ (ppm): -13.57 (q, ⁴ J _PF = 53.4Hz).

¹⁹ F{1H} NMR: 235.39 MHz, CD ₃ OD, δ (ppm): -56.28 (d, ⁴ J _FP = 53.4Hz).

HRMS: ESI m/z

[M-Na ⁺ ] = 477.0155 exp.; 477.0154 calculated for C ₂ oHi ₂ F ₆ 0 ₃ PS.

Sodium 3- henyl(p-trifluoromethylphenyl)phosphino)benzenesulfonate [7-(Na)]

Chemical Formula: Ci ₉ Hi ₃ F ₃ 0 ₃ PSNa Molecular Weight: 432,33

White solid

Freely soluble in water

NMR

1H NMR: 400.13 MHz, CD ₃ OD, δ (ppm): 7.86 (bd, 1H, H _C6 {C ₆ H ₄ S0 ₃ Na}, ³ J _HH = 7.5Hz); 7.85 (bd, 1H, H _C2 {C ₆ H ₄ S0 ₃ Na}, ³ J _HP = 7.3Hz); 7.64 (bd, 2H, H _C3 {C ₆ H ₄ CF ₃ }, ³ J _HH = 7.3Hz); 7.50-7.30 (m, 9H, H _C2 {C ₆ H ₄ CF ₃ } + H _C4 -H _C5 {C ₆ H ₄ S0 ₃ Na} + H _C2 -H _C3 - H _C4 {C ₆ H ₅ }).

¹³ C{1H} NMR: 100.61 MHz, CD ₃ OD, δ (ppm): 146.87 (d, Ci{C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 6.7Hz); 144.18 (d, Ci{C ₆ H ₄ CF ₃ }, ^l ] _c? = 15.1Hz); 138.30 (d, C ₃ {C ₆ H ₄ S0 ₃ Na}, ^l J _c? = 13.6Hz); 136.75 (d, Ci{C ₆ H ₅ }, ^CP = 10.6Hz); 136.54 (d, C ₄ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 20.1Hz); 135.12 (d, C ₂ {C ₆ H ₅ }, ² J _CP = 20.7Hz); 134.84 (d, C ₂ {C ₆ H ₄ CF ₃ }, ² J _CP = 19.4Hz); 132.11 (d, C ₂ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 21.6Hz); 131.67 (q, C ₄ {C ₆ H ₄ CF ₃ }, ² J _CF = 32.3Hz); 130.64 (s, C ₄ {C ₆ H ₅ }); 130.01 (d, C ₃ {C ₆ H ₅ }, ³ J _CP = 7.4Hz); 129.86 (d, C ₅ {C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 6.8Hz); 127.91 (s, C ₆ {C ₆ H ₄ S0 ₃ Na}); 126.26 (dq, C ₃ {C ₆ H ₄ CF ₃ }, ³ J _CP = 6.5Hz - ³ J _CF = 3.8Hz); 125.54 (q, C{CF ₃ }, ^CF = 271.4Hz).

3 ¹ P{1H} NMR: 101.27 MHz, CD ₃ OD, δ (ppm): -3.71 (s).

1 ⁹ F{1H} NMR: 235.39 MHz, CD ₃ OD, δ (ppm): -63.04 (s).

HRMS: ESI m/z 409.0290 exp.; 409.0281 calculated for C ₁₉ H ₁₃ F ₃ O ₃ PS. 3,-((3,5-bis(trifluoromethyl)phenyl)(phenyl)phosphino)benzen esulfonate

Chemical Formula: C ₂ oHi ₂ F ₆ 0 ₃ PSNa Molecular Weight: 500,33

White solid

Freely soluble in water

NMR

1H NMR: 400.13 MHz, CD ₃ OD, δ (ppm): 7.94 (bs, 1H, H _C 4{C ₆ H ₃ (CF ₃ ) ₂ }); 7.91 (m, 1H, Hc ₆ {C ₆ H ₄ S0 ₃ Na}); 7.86 (dtd, 1H, Hc ₂ {C ₆ H ₄ S0 ₃ Na}, ³ J _HP = 8.0Hz - ⁴ J _HH = 1.7Hz - ⁵ J _HH = 0.5Hz); 7.72 (bd, 2H, H _C2 {C6H3(CF ₃ ) ₂ }, ³ J _H p = 6.2Hz); 7.52 (tdd, 1H, Hc ₅ {C ₆ H ₄ S0 ₃ Na}, ³ J _HH = 7.7Hz - ⁴ J _HP = 1.4Hz - ⁵ J _HH = 0.5Hz); 7.49-7.43 (m, 3H, H _C3 - H _C4 {C ₆ H ₅ }); 7.43-7.33 (m, 3H, H _C2 {C ₆ H ₅ } - Hc ₄ {m-C ₆ H ₄ S0 ₃ Na}).

¹³ C{1H} NMR: 90.55 MHz, CD ₃ OD, δ (ppm): 147.23 (d, Ci{C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 7.2Hz); 143.74 (d, Ci {C ₆ H ₃ (CF ₃ ) ₂ }, ^CP = 19.4Hz); 137.11 (d, C ₃ {C ₆ H ₄ S0 ₃ Na}, ^CP = 13.4Hz); 136.46 (d, C ₄ {C ₆ H ₄ S0 ₃ Na}, ² J _CP = 19.6Hz); 135.61 (d, Ci{C ₆ H ₅ }, ^l J _c? = 10.5Hz); 135.11 (d, C ₂ {C ₆ H ₅ }, ² J _CP = 21.1Hz); 134.03 (bd, C ₂ {C ₆ H3(CF ₃ ) ₂ }, ² J _C p = 20.1Hz); 132.91 (qd, C3{C ₆ H3(CF ₃ ) ₂ }, ² J _CF = 33.3Hz - ³ J _CP = 5.6Hz); 132.23 (d, C ₂ {C ₆ H ₄ S0 ₃ Na}, ² JCP = 23.0Hz); 131.22 (s, C ₄ {C ₆ H ₅ }); 130.35 (d, C ₃ {C ₆ H ₅ }, ³ J _CP = 7.5Hz); 130.20 (d, C ₅ {C ₆ H ₄ S0 ₃ Na}, ³ J _CP = 6.8Hz); 128.43 (s, C ₆ {C ₆ H ₄ S0 ₃ Na}); 124.62 (q, C{CF ₃ }, ^CF = 272.1Hz); 123.54 (m, C ₄ {C ₆ H ₃ (CF ₃ ) ₂ }).

3 ¹ P{1H} NMR: 145.78 MHz, CD ₃ OD, δ (ppm): -3.18 (s).

1 ⁹ F{1H} NMR: 235.39 MHz, CD ₃ OD, δ (ppm): -64.98 (s).

HRMS: ESI m/z

[M-Na ⁺ ] = 477.0146 exp.; 477.0154 calculated for C ₂ oHi ₂ F ₆ 0 ₃ PS.

Sodium 3-(phenyl(o-trifluoromethylphenyl)phosphino)benzenesulfonate [9-(Na)] Chemical Formula: CigHnFsOsPSNa

Molecular Weight: 432,33 White solid

Freely soluble in water

NMR

1H NMR: 600.13 MHz, CD ₃ OD, δ (ppm): 7.84 (dt, 1 ³ J _HH = 7.7Hz - ⁴ J _HH = 1.4Hz); 7.82-7.79 (m, 1 H , Hcs dt, 1H, H _C2 {C ₆ H4S03Na} , ³ J _HP = 7.3Hz - ⁴ J _HH = 1.4Hz); 7.56 (bt, 1H, H _C 4 {C6H ₄ CF3}, ³ J _HH = 7.4Hz); 7.52 (bt, 1H, H _C 5 {C ₆ H ₄ CF3}, ³ J _HH = 7.4Hz); 7.44 (td, 1H, Hcs

3J _HH = 7.7Hz - ⁴ J _H p = 1.4Hz); 7.40-7.34 (m, 3H, H _C 3-Hc ₄ {C ₆ H ₅ }); 7.27 (tt, 1H, Hc ₄ {C6H ₄ S03Na}, ³ J _HH = ³ ½> = 7.7Hz - ⁴ J _HH = 1.4Hz); 7.25-7.20 (m, 3H, Hc ₆ {C ₆ H ₄ CF ₃ } + H _C2 {C ₆ H ₅ }).

¹³ C{1H} NMR: 62.90 MHz, CD ₃ OD, δ (ppm): 146.80 (d, Ci {C ₆ H ₄ S0 ₃ Na} , ³ J _CP = 6.2Hz); 138.61 (d, C3 {C ₆ H ₄ S03Na}, ^CP = 14.8Hz); 137.45 (d, C ₆ {C ₆ H ₄ CF3}, ² J _C p =

1.9Hz); 137.21 (d, Ci {C ₆ H ₄ CF ₃ }, ^CP = 30.4Hz); 137.04 (d, d {C ₆ H ₅ }, ^CP = 11.4Hz);

136.25 (d, C ₄ {C ₆ H ₄ S03Na}, ² J _CP = 20.4Hz); 135.81 (qd, C ₂ {C ₆ H ₄ CF3}, ² J _CF = 30.2Hz -

² JCP = 25.5Hz); 134.73 (d, C ₂ {C ₆ H ₅ }, ² J _CP = 20.8Hz); 133.14 (s, C ₅ {C ₆ H ₄ CF3}); 131.86

(d, C ₂ {C ₆ H ₄ S03Na}, ² J _CP = 21.6Hz); 130.66 (s, C ₄ {C ₆ H ₄ CF3}); 130.28 (s, C ₄ {C ₆ H ₅ }); 129.86 (d, C ₃ {C ₆ H ₅ }, ³ J _CP = 7.0Hz); 129.69 (d, C ₅ {C ₆ H ₄ S03Na}, ³ J _CP = 6.6Hz); 127.64

(s, C ₆ {C ₆ H ₄ S03Na}); 127.52 (m, C3 {C ₆ H ₄ CF3}); 125.81 (q, C{CF ₃ }, 'JCF = 274.5Hz).

³¹ P{1H} NMR: 101.27 MHz, CD ₃ OD, δ (ppm): -9.84 (q, ⁴ J _PF = 54.0Hz).

¹⁹ F{1H} NMR: 376.50 MHz, CD ₃ OD, δ (ppm): -55.86 (d, ⁴ J _FP = 52.7Hz).

HRMS: ESI m/z

[M-Na ⁺ ] = 409.0281 exp.; 409.0281 calculated for C ₁₉ H ₁₃ F ₃ O ₃ PS.

Sodium 5-(bis(p-trifluoromethylphenyl)phosphino)-2-metilbenzenesulf onate [10- (Na)]

White solid

Moderately soluble in water

NMR

1H NMR: 400.13 MHz, CD ₃ OD, δ (ppm): 8.03 (dd, 1H, Hce , ³ J _HP = 8.0Hz - ⁴ J _HH = 1.6Hz); 7.69 (bd, 4H, Hc3 {C ₆ H ₄ CF3} , ³ J _HH = 7.8Hz); 7.48 (bt, 4H, H _C2 {C ₆ H ₄ CF3} , ³ J _HH = ³ JHP = 7.8Hz); 7.35 (bd, 1 H, H _C 3 {C ₆ H3(CH3)S03Na} , ³ J _HH =

, ³ J _HP = ³ J _HH = 7.6Hz - ⁴ J _HH = 1.6Hz);

³¹ P{1H} NMR: 161.98 MHz, CD ₃ OD, δ (ppm): -6.18 (s). ¹⁹ F{1H} NMR: 376.50 MHz, CD ₃ OD, δ (ppm): -62.03 (s). HRMS: ESI m/z

[M-Na ⁺ ] = 491.0302 exp.; 491.031 1 calculated for C ₂ iHi ₄ F ₆ 0 ₃ PS

3. Determination of water solubility of trifluoromethylated sulfonated phosphines of Formula (I)

Oversaturated aqueous solutions of the sodium salts of the phosphines of Formula (I) were prepared. The supernatant solution was ultracentrifugated, and then filtered through a nylon filter, a measured weight of this solution was evaporated to dryness and the solid residue was weighed.

The resulting solubilities are showed below:

Phosphine Solubility (g/lOOmL)

1 7 2 70

3 3

4 0.2-1.2

5 0.2-1.2

6 0.2-1.2

7 50

8 >100

9 21

4. Aerial oxidation of the phosphines in aqueous solution

Solutions in distilled water (1 mL, 5 · 10 ^"2 mM ) of the phosphines represented below were prepared with the aim of comparing their inertness against aerial oxidation. The solutions were kept opened to air under vigorous stirring for 120 h. Aliquots were taken and analyzed by ³¹ P{ ¹ H} NMR in order to quantify the oxidation progress. The results show that the presence of trifluormethyl groups decreases the oxidation rate of the phosphine in a factor greater than 10.

Monosulfonated phosphines

Oxidation percentage over time

NaTPPMS 7-(Na) 9-(Na)

Oh 0% 0% 0%

16 h 4% 0% 0%

40 h 25 % 0% 0%

120 h 68 % 4% 0%

Disulfonated phosphines Oxidation percentage over time

NaTPPDS 2-(Na)

O h 0 % 0 %

16 h 6 % 0 %

40 h 33 % 1 %

120 h 100 % 2%

5. Vinyl acetate hydroformylation

Selected sulfonated phosphines here described were tested in the biphasic (water/toluene) hydro formylation of vinyl acetate according to the following experimental procedure: [Rh(acac)(CO) ₂ ] (12.9 mg, 5.0· 10 ^"2 mmol) and the sulfonated phosphine (0.20 mmol) were dissolved in 10 mL of water. Vinyl acetate (4.6 ml, 50.00 mmol) and 0.20 mL of n-dodecane were dissolved in 20 mL of toluene. Solutions were transferred into an autoclave which was purged and filled with 30 bar of syn-gas (1 : 1 H ₂ :CO) at 80°C. After 24 hours, the autoclave was cooled down to room temperature and then the gas was released. The organic phase was separated and the aqueous phase was further extracted with 3 x 5 ml of toluene. The combined organic extracts were analyzed by gas chromatography.

Results are collected in the following table Disulfonated phosphines Monosulfonated phosphines

Ligand (Formula la) (Formula lb)

Na ₂ TPPDS ^a l-(Na) 2-(Na) 3-(Na) NaTPPMS" 8-(Na) 9-(Na)

Conversion

32 99 95 24 20 98 61 (%)

Conditions:

5.0· 10 ^"2 mmol [Rh(acac)(CO) ₂ ], 0.20 mmol ligand, 50 mmol vinyl acetate, 10 ml H ₂ 0, 20 ml toluene, 80°C, 30 bar CO:H ₂ (1 :1), 0.2 ml n-dodecane as internal standard, Conversion reported after 24 h reaction

aNa ₂ TPPDS: PhP(m-C ₆ H ₄ S0 ₃ Na) ₂

NaTPPMS: Ph ₂ P(w-C ₆ H ₄ S0 ₃ Na)

Performed experiments with l-(Na), 2-(Na) and 8-(Na) show that the rate of the reaction is increased by a factor of at least 3 times with respect of the non- trifluoromethylated sulfonated counterparts (i.e. NaTPPMS and Na ₂ TPPDS). Aryl ortho-CF?, substituted phosphines, 3-(Na) and 9-Na are less efficient as co-catalysts than the para and meta CF ₃ substituted phosphines.

High chemo- and regioselectivity to the branched aldehyde (I) were observed in all cases.

6. Nanoparticles stabilization

Platinum nanoparticles of homogeneous size were stabilized in water with the water soluble phosphines here described. Thus, by mixing solutions of K ₂ PtCL( and NaBH ₄ (1- 100 equivalents) or other reducing agents, and a trifluoromethylated sulfonated phosphine of the invention (0.005-2.0 equivalents) nanoparticles were formed after a period of 30 minutes.

In particular, the addition of NaBH ₄ (0.6 mmol) dissolved in 2 ml of water to a solution of K ₂ PtCL( (4· 10 ^"2 mmol) and sulfonated phosphine (0.2 equivalents) in 2 ml of water produce the formation of platinum nanoparticles with an average diameter of 2 nm with a narrow size dispersion, as shown by Transmission Electron Microscopy.