1,3-DIPHOSPHINOPROPANE LIGANDS AND TRANSITION METAL COMPLEXES FORMED THEREFROM, THEIR PREPARATION AND USE

Abstract: In this patent are described 1,3-diphosphinopropane ligands of general formula (I) and their metal complexes to be employed as catalysts for chemical reactions in water or in aqueous media.

Description: 1 ,3-diphosphinopropane ligands and transition metal complexes formed therefrom, their preparation and use Field of the invention The invention relates to compounds of general formula (I) wherein R 1 , R 2 represent hydrocarbyl groups, identical or different from each other, X 1 represents a hydrogen atom, a hydrocarbyl group or a polar group, X 2 represents a polar group, Y represents phosphorus or arsenic and to their preparation and to their use as ligands in metal complexes. The invention further relates to coordination compounds that the ligands of formula (I) form with transition metals, to their preparation and to their use as molecular catalysts for reactions in water or in polyphasic systems comprising an aqueous phase, or as heterogeneous catalysts obtained by anchoring their metal complexes to common inorganic and organic supports (silica, alumina, pumice, organic polymers). State of the art It is well-known that many chemical reactions require the presence of a catalyst, generally a metal complex, to take place with high rate and selectivity. For reactions in aqueous media or in polyphasic systems wherein water is the polar phase, it is necessary for the catalyst to be water-soluble. Among the transition metal complex catalysts involved in a large variety of reactions, the most common are those which contain a metal centre coordinated by mono- or polydentate phosphine ligands with different hydrocarbyl substituents on the P-donor atoms. A common strategy for achieving the solubility in water of the ligands involves the introduction of a polar group on one or more substituents on the donor atoms (in the case of phosphorus donors, this is generally achieved by sulfonation of aryl substituents). Ligands and complexes of the types mentioned above and their application to catalysis are described in: Applied Homogeneous Catalysis with Organometallic Compounds, B. Corniis and W. A. Herrmann, Eds.; VCH: Weinheim, Germany 1996, Vol. 2, Chapter 3.1 , pp. 573-623. In the water-soluble phosphine ligands of current use in catalysis, the donor atoms are sterically congested and, eventually, electronically deactivated by the polar substituents, however these two effects may decrease the coordination capability of the ligands as compared to similar ligands devoid of the functional group(s) which allow them to be water-soluble. Moreover, the majority of the known water- soluble ligands are unidentate and the selectivities (chemo-, regio- and stereoselectivity) induced by their metal catalysts are generally poor. The stability of these complexes towards ligand dissociation pathways is also rather low. A few water-soluble bidentate ligands are known. In none of them, however, the phosphorus donors are separated by three CH 2 groups and the phosphorus substituents do not bear polar groups. Detailed description of the invention The invention allows one to overcome the problems occasioned by the proximity of the donor atoms and the polar groups by using metal complexes with either 1 ,3- diphosphinopropane or 1,3-diarsinopropane ligands in which the polar group(s) is (are) bound, directly or by means of an appropriate substituent, to the carbon in the 2-position of the propylenic chain in between the two phosphorus or arsenic atoms. The ligands which are the object of the invention, have the formula (I): wherein X 1 , X 2 , R 1 , R 2 and Y are defined as reported above. The metal complexes obtainable with these ligands exhibit the following advantages over the known water-soluble ligands: decreased steric hindrance at the donor atoms, which allows the formation of a wider range of stable water- soluble transition metal complexes; increased capability of inducing chemo-, regio- and stereoselective reactions; increased stability of the resulting metal complexes (polydentate effect); possibility of introducing the ligating group (phosphine or arsine) into the ligand framework after the water-soluble molecular structure has already been assembled, and, consequently, possibility of using a wider range of phosphorus or arsenic substituents; possibility of anchoring both ligands and metal complexes on common inorganic and organic supports, and thus eventual application of the supported complexes to heterogeneous catalytic reactions (liquid-solid and gas-solid). Within the context of the present invention, for hydrocarbyl group we mean: a linear alkyl group, branched or cyclic, containing from 1 to 6 carbon atoms, or an aryl group, generally alkyl-substituted; for polar group we mean: one of the polar groups commonly employed for making a ligand soluble in water (alkyl- or arylsulfonate; hydroxy, tetraalkyl(or aryl) ammonium salt; carboxylate). Preferably, the alkyl group on the phosphorus donor is the cyclohexyl one (-C 6 H n ), the aryl group is the phenyl one (-C 6 H 5 ), the polar group is p-benzylsulphonic or p- benzylsulphonate (as alkali salt) (-CH 2 (C 6 H 4 )S0 3 H, or -CH 2 (C 6 H 4 )S0 3 - Na + , K + , Li + ). The ligands which are the object of the invention can be prepared as exemplified in the procedure shown in the Scheme. As is apparent from the Scheme, the synthetic strategy for all the diphosphine or diarsine ligands involves as starting compound diethylmalonate or its derivatives obtained by changing the substituent on the central carbon atom. The introduction of the polar group(s) is achieved by ordinary chemical reactions in common organic solvents. In a similar way, the introduction of the donor atoms (P or As) is achieved by reaction between phosphide or arsenide groups and bis-halide compounds already containing the polar group(s). The ligands obtained in this way are able to coordinate every transition metal in various oxidation states. The complex-formation reactions take place via the common methods of coordination chemistry, for example by displacement of labile ligands from their complexes or by reaction between the ligands and inorganic salts of the metals (generally halides). The following example details the preparation of a 1 ,3-diphosphinopropane ligand of the formula (Na0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 [2,2-bis(p-Na-sulfonato-benzyl)- 1 ,3-diphenylphosphinopropane] (quoted in the Scheme as la). EXAMPLE Synthesis of (PhCH 2 V,C(C0 2 Etl, (2.2-bis(ethylcarboxylateV-1.3-diphenylpropane. To a solution of PhCH 2 CH(C0 2 Et) 2 (74.1 g, 0.30 mol) in tetrahydrofuran (THF) (150 mL) at 0 °C under an inert atmosphere (N 2 or Ar) was added portionwise with stirring NaH (60 % suspension in mineral oil, 13.6 g, 0.34 mol). After a clear solution was obtained (ca. 1 h), 58.2 g (0.34 mol) of benzyl bromide in 50 mL of THF was added dropwise in 1 h. Afterwards, the reaction mixture was allowed to reach room temperature, stirred for ca. 15 h and then hydrolyzed with an aqueous solution of NH 4 CI (16 g in 200 mL of water) to give two phases. The organic phase was separated and set aside. The aqueous layer was washed three times with ethyl ether. After the washings were poured into the organic phase, the resulting solution was treated with sodium sulfate to remove water and pumped to dryness. The oily residue was distilled under reduced pressure to give 91 g of (PhCH 2 ) 2 C(C0 2 Et) 2 (93% yield); b.p.: 190 °C (0.1 torr). 1 H NMR (CDCI 3 , 20 °C, 200.13 MHz): d 7.4-7.1 (m, 10 H, Ph), 4.12 (q, 4 H, J(HH) = 7.2 Hz, CH 2 CH 3 ), 3.24 (s, 4 H, CH 2 Ph), 1.17 (t, 6 H, J(HH) = 7.2 Hz, CH 2 C± . Synthesis of tPhCH 2 ) 2 C(CH,OH (2.2-bis(benzvn-1.3-propandiol. A solution of (PhCH 2 ) 2 C(C0 2 Et) 2 (30 g, 0.09 mol) in ethyl ether (150 mL) was poured by means of a dropping funnel into a suspension of LiAIH 4 (10 g) in 150 mL of ethyl ether at 0 °C under an inert atmosphere with vigorous stirring. The resulting reaction mixture was then allowed to warm to room temperature, refluxed for 2 h, cooled again to 0 °C and, finally, poured slowly into an aqueous solution of HCI (3.4 M) maintained at 0 °C. The mixture was transferred to a separatory funnel. The ether phase was separated, washed several times with distilled water and then treated with sodium sulfate to remove water. Upon removal of the solvent under reduced pressure, (PhCH 2 ) 2 C(CH 2 OH) 2 was obtained as an off- white solid (20.3 g, 90 % yield). 1 H NMR (CDCI 3 , 20 °C, 200.13 MHz): d 7.3-7.1 (m, 10 H, Ph), 3.57 (d, 4 H, J(HH) = 5.2 Hz, CH 2 OH), 2.76 (s, 4 H, CH 2 Ph), 1.93 (t, 2 H, J(HH) = 5.2 Hz, CH 2 OH). Synthesis of (PhCH,) z C(CH,CI) (2.2-bis(benzvn-1.3-dichloropropane. To a solution of (PhCH 2 ) 2 C(CH 2 OH) 2 (14.4 g, 0.06 mol) in 40 mL of anhydrous pyridine at 0 °C was added with stirring under an inert atmosphere 16 mL (26 g, 0.21 mol) of SOCI 2 in ca. 2 h. The resulting mixture was refluxed for 2 h and then stirred at room temperature for 15 h. After cooling to 0 °C, equal volumes of CH 2 CI 2 and water (200 mL each) were added to the reaction mixture. The separated organic layer was washed with an aqueous solution of HCI (pH 4) and then with distilled water. After the CH 2 CI 2 solution was treated with sodium sulfate, the solvent was removed under reduced pressure. To the resulting oily residue was added ethyl ether (30 mL) until an off-white solid precipitated, which was recrystallized from ethanol to give 10 g of crystalline (PhCH 2 ) 2 C(CH 2 CI) 2 (61% yield). H NMR (CDCI 3 , 20 °C, 200.13 MHz): d 7.5-7.2 (m, 10 H, Ph), 3.23 (s, 4 H, CH 2 CI), 2.91 (s, 4 H, CH^Ph). dichloropropane. A suspension of (PhCH 2 ) 2 C(CH 2 CI) 2 (5.6 g, 19 mmol) in 25 mL of 96 % H 2 S0 4 was stirred at 100 °C for 3 h under inert atmosphere, then for 15 h at room temperature. To the resulting mixture, cooled to 0 °C, were added cold water (200 mL) and then a cold aqueous 20 % solution of NaOH until a neutral, brown solution was obtained. This was concentrated under reduced pressure to 100 mL. Upon addition of MeOH (40 mL), sodium sulfate precipitated. All the salt material was filtered off after 15 h. The remaining solution was evaporated under reduced pressure to give an oily residue which transformed into off-white crystals of (Na0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 CI) 2 upon addition of ethanol (30 mL). Yield 4 g, 42 %. Η NMR (CDCI 3 , 20 °C, 200.13 MHz): d 7.69 (d, 4 H, J(HH) = 8.3 Hz, o- (C 6 H 4 )S0 3 Na), 7.37 (d, 4 H, J(HH) = 8.3 Hz, m-(C 6 H 4 )S0 3 Na), 3.14 (s, 4 H, CH 2 CI), 2.86 (s, 4 H, (C R H 4 )CH 2 ). Synthesis of iNaOoSf H/lCH CfCH PPh l, (2.2-bis(p-Na-surfonato-benzvn-1.3- diphenyphosphinopropane. To a solution of KPPh 2 , obtained by reacting KOBu' (2.3 g, 20.6 mmol) with a solution of HPPh 2 (3.8 g, 20.6 mmol) in 50 mL of dimethyl sulfoxide at room temperature under an inert atmosphere, was added dropwise 30 mL of a solution of (Na0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 CI) 2 (4.3 g, 8.65 mmol) in dimethy sulfoxide. After the resulting orange solution was heated at 100 °C for 5 h, the solvent was removed under reduced pressure to give a yellow oily residue. Treatment of this latter with a saturated solution of NaCI (100 mL) under vigorous stirring gave (Na0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 as an off-white solid which was recrystallized from a 1 :1 mixture (vv) of methanol/ethanol; 6 g, 87 % yield. 31 P{ 1 H} NMR (MeOH- d 4l 20 °C, 81.01 MHz): d 27.2 (s). 1 H NMR (MeOH-d 4 , 20 °C, 200.13 MHz) d 7.55 (d, 4 H, J(HH) = 8.2 Hz, o-(C 6 H 4 )S0 3 Na), 7.3-7.1 (m, 20 H, Ph), 7.14 (d, 4 H, m- (C 6 H 4 )S0 3 Na), 2.89 (s, 4 H, (C-βHJCH g ), 1.93 (br d, 4 H, J(HP) = 2.7 Hz, CH 2 PPh 2 ). Through procedures which are analogous to that described above for (Na0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 (or through alternative, ordinary organic reactions) using appropriate reagents, the following products were similarly obtained: (M0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 YR 1 R 2 ) 2 where Y = P, As; R , R 2 = CH 3 , C 2 H 5 , '-C.Hg, C β H 11 f C 6 H 5 ; M = H, Li, Na, K. M0 3 S(C 6 H 4 )CH 2 CRC(CH 2 YR 1 R 2 ) 2 where Y = P, As; R = H, CH 3 ; R 1 , R 2 = CH 3 , C 2 H 5 , C β H 11 f C 6 H 5 ; M = H, Li, Na, K. The ligands described above were employed for the preparation of metal complexes, either in situ or isolated, with transition metals, particularly with Pd, Rh, Ir, Ru, Pt, Ni, Co in various oxidation states and coordination numbers. These complexes have been employed directly or after their anchoring on appropriate inorganic and organic supports, as catalysts in various known reactions in aqueous media, in liquid-biphase systems (in which one phase is water), or in heterogeneous systems (liquid-solid). Some examples are given below: Alternate copolvmerization of CO and ethene in water. The use of catalytic amounts of either Na 2 [{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Pd(0 2 CCR 3 ) 2 ] (R = H, F) or of (Na0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 and Pd(0 2 CCR 3 ) 2 (R = H, F) in the presence of a 200-fold excess of trifluoroacetic acid (acid to catalyst ratio = 200) gave the polyketone copolymer with a productivity of 7.8 Kg of copolymer per g of Pd (68 bar, 1 :1 carbon monoxide/ethene; 85 °C). Terpolvmerization of CO. ethene and propene in water. The use of catalytic amounts of either Na 2 [{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Pd(0 2 CCR 3 ) 2 ] (R = H, F) or of (Na0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 and Pd^CCR^J (R = H, F) in the presence of a 200-fold excess of trifluoroacetic acid (acid to catalyst ratio = 200) gave the terpolymer with a productivity of 4.9 Kg of terpolymer per g of Pd (68 bar, 1 :1 carbon monoxide/ethene;10 g liquid propene ; 85 °C). Hvdroformylation of alkenes in liquid-biphase systems. The hydroformylation of 1-hexene was carried out in water//-octane with a 1 :1 mixture of CO and H 2 (30 bar) in the presence of catalytic amounts of Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Rh(H 2 0) 2 ] with the following results: total conversion 95.3 %, aldehydes 59.8 %, iso/n = 1.4 (substrate:catalyst = 100; 5 h, 80°C). Reduction of ketones to alcohols in liquid-biphase systems. The hydrogenation (15 atm H 2 ) of trans-PhCH=CH(COMe) was carried out in water/n-hexane in the presence of catalytic amounts of (Na0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 and RuCI 3 6H 2 0 with the following results: PhCH 2 CH 2 (COMe) 88 %, PhCH 2 CH 2 CH(OH)Me (12 %) (substrate atalyst = 100; 5 h; 100°C). Reduction of alkenes in heterogeneous systems. After anchoring the complex Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Rh(H 2 0) 2 ] over activated Si0 2 (Davinson, ca. 200 m 2 /g) using standard procedures, a catalytic amount of the resulting solid was used in a hydrogenation reaction of styrene which was totally converted to ethylbenzene after 2 h (substrate:catalyst = 100; 30 bar H 2 ; 100°C). H R ^ \ /~ * YR1R2

Claims: Claims 1. Compounds of formula (I) wherein R and R 2 represent hydrocarbyl groups, identical or different from each other, X 1 is chosen from the group consisting of: hydrogen atom, a hydrocarbyl group or a polar group, X 2 represents a polar group, Y is chosen from the group consisting of phosphorus and arsenic. 2. Compounds as claimed in claim 1 characterized in that the hydrocarbyl group is a linear, branched or cyclic alkyl group containing from 1 to 6 carbon atoms or an aryl group possibly alkyl-substituted. 3. Compounds as claimed in claim 2 characterized in that the polar group is chosen from the group consisting of: aryl- or alkyl-sulfonic acid , sulfonate alkali salt (-S0 3 H, -S0 3 ' M + wherein M + is Li, Na, K), a hydroxy group (-OH) and a quaternary ammonium salt. 4. Compounds as claimed in claim 3 as indicated below: (M0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 YR 1 R 2 ) 2 wherein Y = P, As,; R\ R 2 = aryl, linear, branched or cyclic alkyl containing up to 6 carbon atoms; M = H, Li, Na, K. M0 3 S(C 6 H 4 )CH 2 CR(CH 2 YR 1 R 2 ) 2 wherein Y = P, As; R = H, Me; R 1 , R 2 = aryl, linear, branched or cyclic alkyl containing up to 6 carbon atoms; M = H, Li, Na, K. 5. Use of the compounds of the general formula (I) as claimed in claim 1 for the preparation of complexes with transition metals. 6. Complexes consisting of a transition metal and at least one compound as claimed in claim 1. 7. Complexes, isolated or generated in solution, as claimed in claim 6 characterized in that the transition metal is chosen in the group consisting of: Pd, Rh, Ir, Ru, Pt, Ni, Co in various oxidation states and coordination numbers. 8. Complexes as claimed in claim 6 indicated as follows: Na 2 [{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Pd(0 2 CCR 3 ) 2 ] (R = H, F), Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Rh(H 2 0) 2 ], Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Rh(COD)] (COD = 1 ,5-cyclooctadiene), Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }lr(COD)], [{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 } 2 Ru(H 2 0) 2 ]. 9. Process for the preparation of the compounds as claimed in claim 1 characterized in that the preparation is carried out by the reaction between the 1 ,3-dihalopropane product substituted in the 2-position with one or more polar groups and bis-organyl-substituted phosphide or arsenide alkali salt. 10. Use of the complexes as claimed in claim 6 either as catalysts in reactions carried out in aqueous media or polyphasic systems in which the polar phase is water, or as heterogeneous catalysts (liquid-solid reactions) after the metal complexes have been anchored to appropriate inorganic or organic supports. 11. Process wherein the the complexes as claimed in claim 6 are used either as catalysts in reactions carried out in aqueous media or polyphasic systems in which the polar phase is water, or as heterogeneous catalysts (liquid-solid reactions) after the metal complexes have been anchored to appropriate inorganic or organic supports. 12. Use as claimed in claim 10 of the complex Na 2 [{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Pd(0 2 CCR 3 ) 2 ] (R = H, F) in reactions of co- polymerization of CO/alkenes, terpolymerization of CO/ethene/alkenes, telomerization and hydrodimerization of alkenes and dienes, metathesis of alkenes, reactions of alkenes with alkyl and aryl halides and pseudohalides (Heck reactions). 13. Process according to Claim 11 wherein such process is a process of co- polymerization of CO/alkenes, terpolymerization of CO/ethene/alkenes, telomerization and hydrodimerization of alkenes and dienes, metathesis of alkenes, reactions of alkenes with alkyl and aryl halides and pseudohalides (Heck reactions) comprising the use of the complex Na 2 [{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Pd(0 2 CCR 3 ) 2 ] (R = H, F) 14. Use of the complex Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Rh(H 2 0) 2 ] in hydrogenation and hydroformylation reactions of alkenes. 15. Process according to claim 11 wherein such process is a process of hydrogenation and hydroformylation of alkenes comprising the use of the complex Na[{(0 3 S(C e H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Rh(H 2 0)J. 16. Use of the complex Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Rh(COD)] (COD = 1 ,5- cyclooctadiene) in hydrogenation and hydroformylation reactions of alkenes. 17. Process according to Claim 15 comprising the use of the complex Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }Rh(COD)] (COD = 1 ,5-cyclooctadiene) 18. Use of the complex Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }lr(COD)] in reactions of reduction of saturated and unsaturated ketones. 19. Process according to Claim 11 wherein such process is a process of reduction of saturated and unsaturated ketones comprising the use of the complex Na[{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 }lr(COD)]. 20. Use of the complex [{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 } 2 Ru(H 2 0) 2 ] in the following reactions: reduction of ketones, of imines, of enamines, of nitriles, and of nitrogen heterocycles (pyridines, quinolines, pyrazoles, carbazoles). 21. Process according to Claim 11 wherein such process is a process of reduction of ketones, of imines, of enamines, of nitriles, and of nitrogen containing heterocycles (pyridines, quinolines, pyrazoles, carbazoles) comprising the use of the complex [{(0 3 S(C 6 H 4 )CH 2 ) 2 C(CH 2 PPh 2 ) 2 } 2 Ru(H 2 0) 2 ].

Inventors: BIANCHINI CLAUDIO, MELI ANDREA, VIZZA FRANCESCO, BIANCHINI, CLAUDIO, MELI, ANDREA, VIZZA, FRANCESCO
Applicants: BIANCHINI CLAUDIO, CONSIGLIO NAZIONALE RICERCHE, MELI ANDREA, VIZZA FRANCESCO, BIANCHINI, CLAUDIO, CONSIGLIO NAZIONALE DELLE RICERCHE, MELI, ANDREA, VIZZA, FRANCESCO
Application year: 1997
Main classification: C07F9
IPC codes: B01J31, C07C5, C07C17, C07C29, C07C45, C07F9, C07F15