Abstract:
New palladium-based complexes permit the complexing of chlorinated aromatic derivatives. These complexes make it possible to perform hydrogenolysis, hydrocarbonylation and alkoxycarbonylation reaction on chlorinated compounds.

Description:
FIELD OF THE INVENTION 
     The present invention relates to new complexes, and more particularly to new palladium-based complexes. The present invention relates more particularly to the formation of complexes of palladium and of chlorinated aromatic compounds. 
     BACKGROUND OF THE INVENTION 
     Complexes of palladium and of triphenylphosphine have been known for a very long time. For example, the preparation and the use of complexes based on palladium and triphenylphosphine are described by Heck in U.S. Pat. Nos. 3,960,932 and 3,988,358. These complexes permit carbonylation reactions of aromatic bromo or iodo compounds, but do not permit in any circumstance the carbonylation of chlorinated aromatic compounds. 
     When one skilled in the art, reading the prior art, attempted to carbonylate aromatic compounds in a homogeneous medium, it was always necessary to start with aromatic bromo or iodo compounds and then to complex them with a complex palladium salt. It has also been known for a very long time that brominated aromatic compounds are much more costly in price than chlorinated compounds. The problem of carbonylation of chlorinated aromatic compounds is a problem which the present invention has attempted to solve. 
     DESCRIPTION OF THE INVENTION 
     The new complexes of the present invention correspond to the following formula (I): ##STR1## in which 
     Ar is a substituted mono- or polycyclic or heterocyclic aromatic radical, 
     each of R 1 , R 2 , and R 3  is an identical or different group selected from cyclohexyl, benzyl and isopropyl radicals, it being possible for one of groups R 1 , R 2 , and R 3  to be replaced by a phenyl group when the other two are cyclohexyl groups, and 
     n is an integer equal to 0 or 1. 
     The complexes of formula (I) of the present invention are prepared by at least three methods of preparation. 
     According to a first method of preparation, a compound of the following formula (II): ##STR2## in which 
     the moiety L is a group which is labile in the presence of ArCl, and 
     the groups R 1 , R 2 , and R 3  have the same meaning as in formula (I), is brought into contact with an aromatic halo compound of the formula ArCl and optionally with carbon monoxide when n is other than 0. 
     According to a second method of preparation of complexes of formula (I), 
     1. a complex of palladium in the zero oxidation state selected from either: ##STR3## or Pd(L) 3  in the presence of at least two equivalents of phosphine corresponding to the formula ##STR4## is brought into contact with 
     2. the chloroaromatic compound of the formula ArCl and, optionally carbon monoxide when n is other than zero. 
     According to a third method of preparation of the complexes of formula (I), a salt of palladium in the oxidation state II selected for example, from palladium dichloride, dibromide or diiodide, palladium diacetate, palladium nitrate, palladium sulfate and palladium oxide, is brought into contact with the chloroaromatic compound and at least two equivalents of a phosphine of formula ##STR5## in the presence of a reducing agent consisting of hydrogen and optionally in the presence of carbon monoxide when n is other than zero. 
     Within the scope of the present invention, a labile group (L) means any group which can be easily exchangeable in the presence of ArCl. 
     Among these groups there may be mentioned, no limitation being implied: 
     dibenzylideneacetone (DBA) 
     alkylene, and preferably ethylene, groups. 
     In all the above-mentioned preparative procedures, it is preferred to operate in an organic solvent selected from 
     aromatic solvents such as benzene, toluene and xylenes 
     aliphatic solvents 
     ethers such as diisopropyl ether 
     amides such as dimethylformamide 
     nitriles such as benzonitrile. 
     The chlorinated aromatic compound can also be used as a reaction medium. 
     As stated above, when starting with a palladium complex which does not contain any phosphine, it is preferred to use at least 2 moles of phosphine per atom of palladium and more preferably from 2 to 5 moles. 
     It is preferred to employ a quantity of solvent such as to make the concentration of palladium complex or salt in the medium from 1 to 100 mmols per liter. 
     The temperature at which the reactants are brought into contact is preferably from ambient temperature to 200° C. The duration of contact will vary with the temperature, but a duration of from one hour to approximately a day appears to be preferred. 
     When n is other than zero, that is, when the complex of formula (I) contains at least one --CO-- group, the preparation of this compound is carried out in the presence of carbon monoxide. The pressure of carbon monoxide of from 1 to 50 bars is preferred. 
     The complex of formula II, used as a starting material for the synthesis of the complex of formula I in which L is dibenzylideneacetone (DBA), is a new product which is claimed as such. It corresponds to the following formula III: ##STR6## in which R 1 , R 2 , and R 3  have the same meaning as above. 
     It is used for the preparation of the complex of formula I. It is prepared by bringing dibenzylidene acetone - palladium, a complex salt, into contact with at least 2 equivalents of a phosphine of the formula ##STR7## in an organic solvent. 
     The organic solvent is the same as that which can be used for the synthesis of the complexes of formula I. 
     The complexes of formula I which are obtained within the scope of the present invention are employed especially in hydrogenolysis, hydrocarbonylation or alkoxycarbonylation reactions, such as described in patent applications filed concurrently with the present application. 
     The application will be described more completely with the aid of the following examples which must not in any event be considered as limiting the invention. 
     In the following examples, the abbreviations employed have the following meanings: 
     DBA=dibenzylideneacetone 
     Cy=cyclohexyl 
     Bz=benzyl 
     Ph=phenyl 
    
    
     EXAMPLE 1 
     Pd (DBA) (PCy 3 ) 2  ←Pd(DBA) 3  +2 PCy 3   
     500 mg (0.55 mM) of Pd(DBA) 3  and 458 mg (1.65 mM, that is a 50% excess) of PCy 3  were dissolved in 50 ml of benzene. The solution of the mixture was heated to 50° C. for 16 hours and the metallic palladium formed was then separated off by filtration; after the filtrate had been evaporated to dryness, the orange-colored solid thus obtained was washed with 40 ml of ether to extract the excess DBA and phosphine. A yellow powder (342 mg, Y=70%) was isolated and characterized by NMR ( 1  H and  31  P and IR). 
     IR (nujol) (ν cm -1 ): 1640 (C=O); 1575 and 1585 (C=C).  1  H NMR(200 MHz, C 6  D 6 ) δ (ppm): 1.3 to 2.3 (m, 66H, aliphatic protons of PCy 3 ); 7.1 to 7.7 (m, 10H, aromatic H of DBA); 5.1 (m, 2H, olefinic protons); 8.2 (m, 2H, olefinic protons).  31  P-[ 1  H]NMR (80 MHz, C 6  D 5  CD 3 ) δ: 35 ppm. 
     EXAMPLE 2 
     Pd(PCy 3 )(C 6  H 5 )Cl←Pd(DBA) (PCY 3 ) 2  +C 6  H 5  Cl 
     1.3 g (1.44 mM) OF PD(DBA)(PCy 3 ) 2  were dissolved in 100 ml of chlorobenzene. The solution was kept stirred at 60° C. for 2 hours and was then filtered to remove the traces of metallic palladium. After the filtrate had been evaporated down, the solid thus obtained was washed with 50 ml of ether to extract the DBA released during the reaction. 850 mg (1.09 mM, Y=76%) of a white product were isolated. 
     IR(nujol) ν (cm -1 ): 705 and 740 (monosubstituted aromatic C--C). 
       1  H NMR(200 MHz, C 6  D 6 ) δ (ppm): 7.74 (d, 1H, ortho aromatic hydrogen); 7.13 (t, 2H, meta aromatic hydrogens; 7.00 (t, 2H, para aromatic hydrogens); 1.2 to 2.35 (m, 66H, aliphatic protons of PCy 3 ). 
       31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm): 22.9 (s). 
     EXAMPLE 3 
     Carbonylation of the Pd(PCy 3 ) 2  (C 6  H 5 )Cl complex 
     Pd(PCy 3 ) 2  (C 6  H 5 )Cl+CO→C 6  H 5  CO.Pd(PCy 3 ) 2  Cl 
     150 mg (0.2 mM) of Pd(PCy 3 )2(C 6  H 5 )Cl were dissolved in 15 ml of benzene and were placed in an autoclave under 30 bars of CO. The colorless solution stirred at ambient temperature quickly turned yellow, but reaction was complete only after 20 hours. After filtration and evaporation of the filtrate, a yellow product (120 mg, Y=75%) was isolated. 
     IR(nujol) ν (cm -1 ) 1630 (C═O). 
       1  H NMR (200 MHz,m C 6  D 6 ) δ (ppm): 7.47, 7.95 and 9.60 (broad peaks, 5H, aromatic protons); 1.05 to 2.60 (m, 66H, aliphatic protons of PCy 3 ). 
       31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm): 22.4 (s). 
     EXAMPLE 4 
     Synthesis of the Pd(PCy 3 ) 2  (C 6  H 5 )Cl complex in one stage from Pd(DBA) 3   
     A solution containing 13.8 g (17 mmol) of Pd(DBA) 3  and 10.5 g (37.5 mmol, that is a 10% excess) of tricyclohexylphosphine in 400 ml of freshly distilled and degassed chlorobenzene was stirred for 2 hours at ambient temperature and was then heated to 55° C. for 16 hours. The dark-yellow solution thus obtained was filtered slowly to remove the traces of metallic palladium and was then evaporated to dryness. The yellow solid was washed with 200 m of ether to dissolve the DBA released during the reaction and the excess phosphine, and then with 20 ml of THF to remove the traces of unconsumed Pd(DBA) 3 , and finally with 100 ml of ether. The white product (10.8 g, 13.9 mmol, Y=82%) was dried under vacuum and analyzed by IR,  1  H and  31  P NMR. 
     IR(nujol) ν (cm -1 ): 705 and 740 (monosubstituted aromatic C--C).  1  H NMR (200 MHz, C 6  D 6 ) δ (ppm) : 7.74 (d, 1H, ortho aromatic hydrogen); 7.13 (t, 2H, meta aromatic hydrogens); 7.00 (t, 2H, para aromatic hydrogens); 1.2 to 2.35 (m, 66H, aliphatic protons of PCy 3 ). 
       31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm): 22.9 (s). 
     EXAMPLE 5 
     Pd(DBA)(PPhCy 2 ) 2  ←Pd(DBA) 3  +2PPhCy 2   
     A solution containing 970 mg (3.53 mmol) of PCy 2  Ph and 1.27 g (1.57 mmol) of Pd(DBA) 3  in 50 ml of toluene was stirred for 3 hours at ambient temperature. After evaporation of the solvent, the orange-colored solid was washed with ether to dissolve the DBA released during the reaction and the slight excess of phosphine; 950 mg (1.07 mmol, Y - 84%) of an air sensitive orange-colored product was isolated. 
     IR(nujol) ν (cm -1 ): 1640 (C═O).  1  H NMR (200 MHz, C 6  D 6 ) δ (ppm): 0.5-2.7 (m, 44H, Cy); 5.35 (m, 2H, olefinic H); 8.1 (m, 2H, olefinic H); 6.9-7.7 (m, 20H, aromatic H).  31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm): 31.7 (broad s). 
     EXAMPLE 6 
     Pd(DBA) (PBz 3 ) 2  ←Pd(DBA) 3  +2 PBz 3   
     A solution containing 2.13 g (2.63 mmol) of Pd(DBA) 3  and 1.74 g (5.72 mmol, 10% excess) of PBz 3  in 150 ml of toluene was stirred for 2h 30 min at ambient temperature and was then evaporated to dryness. The solid thus obtained was washed with 100 ml and then twice with 20 ml of ether, which made it possible to isolate 1.85 g (1.95 mmol, Y=74%) of a yellow product. 
     IR(nujol) ν (cm -1 ): 1640 (C═O).  1  H NMR (200 MHz, C 6  D 6 ) δ (ppm): 5.01 (d,  3  J H-H  =10 Hz, 1H, olefinic H); 5.66 (d,  3  JH-H =10 Hz, 11H, olefinic H); 6.74 (d,  3  J H-H  =15 Hz, 1H, olefinic H); 7.87 (d,  3  J H-H  =15 Hz, 1H, olefinic H); 2.81 (d,  2  J H-P  =5 Hz, 12 H, CH 2  Ph); 7.1-7.5 (m, 40H, aromatic H).  31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm): 11.9 (broad s). 
     EXAMPLE 7 
     Pd(PCy 2  PH) 2  (C 6  H 5 )Cl←Pd(DBA) (PCy 2  Ph) 2  +C 6  H 5  Cl 
     An orange-colored solution of the complex Pd(DBA)(PCy 2  PH) 2  in 30 ml of chlorobenzene heated to 80° C. for 30 min quickly turned pale yellow. After the evaporation of the solvent to dryness, the product formed save for DBA was analyzed by NMR. 
       1  H NMR (200 MHz, C 6  D 6 ) δ (ppm): 1.1-2.7 (m, 44H,Cy); 6.9 (m, 3H, meta and para H of PdC 6  H 5 ); 7.15-7.25 (m, 6H, meta and para H of P-C 6  H 5 ); 7.53 (d, 2H, ortho H of PdC 6  H 5 ); 7.7-7.8 (m, 4H, ortho H of P-C 6  H 5 ).  31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm): 24.4 (s). 
     EXAMPLE 8 
     Pd(PBz 3 ) 2  (C 6  H 5 )Cl←Pd(DBA) (PBz 3 ) 2  +C 6  H 5  Cl 
     A solution containing 500 mg of Pd(DBA)(PBz 3 ) 2  in 100 ml of chlorobenzene was heated to 80° C. for 3 hours and was then evaporated to dryness. The solid residue was washed with ether and dried under vacuum. A slightly greyish product was isolated. 
       1  H NMR (200 MHz, C 6  D 6 ) 6 (ppm): 3.25 (t, 12H,  2  J H-P  + 4  J H-P  =6Hz, CH 2  -C 6  H 5 ); 6.7-7.55 (m, 35H, aromatic H).  31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm): 12.5 (s). 
     EXAMPLE 9 
     Pd(PCy 3 ) 2  (C 6  H 4  COOEt)Cl←Pd(DBA)(PCy 3 ) 2  +ClC 6  H 4  COOEt 
     10 ml of ClC 6  H 4  COOEt were added to a solution containing 380 mg (0.42 mmol) of Pd(DBA)(PCy 3 ) 2  in 30 ml of toluene. After 10 minutes of stirring at 80° C., the mixture had turned from red to yellow. After evaporation of the solvent, a white solid was precipitated with acetone and was then isolated by filtration. 210 mg of an air-stable complex (0.25 mmol, Y=59%) was isolated. 
     IR(nujol) ν (cm -1 ): 1710 (C═O).  1  H NMR (200 MHz, C 6  D 6 ) δ (ppm): 1.14 (t, J=7Hz, 3H, CH 3 ); 4.26 (q, J=7Hz, 2H, CH 2  CH 3 ); 1.1-2.45 (m, 66H, PCy3); 7.91 (d, J=8Hz, 2H, arom. H); 8.18 (d, J=8Hz, 2H, arom. H).  31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm) : 23.1 (s). 
     EXAMPLE 10 
     Pd(PCy 3 ) 2  (C 6  H 4  OCH 3 )Cl←Pd(DBA)(PCy 3 ) 2  +ClC 6  H 4  OCH 3   
     The synthesis was performed under the same conditions as in Example 9. A reaction time of one hour was needed, however, to obtain quantitatively an airstable white product. 
       1  H NMR (200 MHz, C 6  D 6 ) δ (ppm): 1.1-2.45 (m, 66H, PCy 3 ); 3.58 (s, 3H, OCH3); 6.90 (d, J=8Hz, 2H, arom. H); 7.57 (d, J=8Hz, 2H, arom. H).  31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm): 23.1 (s). 
     EXAMPLE 11 
     Pd(PCy 3 ) 2  (C 6  H 4  NO 2 )Cl←Pd(DBA) (PCy 3 ) 2  +ClC 6  H 4  NO 2   
     A solution containing 500 mg (0.55 mmol) of Pd(DBA)(PCy 3 ) 2  and 1 g (6.35 mmol) of ClC 6  H 4  NO 2  in 50 ml of toluene was heated for 1 hour to 80° C. After evaporation of the solvent, the solid was washed with acetone, which resulted in 420 mg of a white product (0.51 mmol, Y=93%). 
       1  H NMR (200 MHz, C 6  D 6 ) δ (ppm): 0.9-2.3 (m, 66H, PCy 3 ); 7.70 (d, J=8Hz, 2H, arom. H); 8.03 (d, J=8Hz, 2H, arom. H).  31  P-[ 1  H]NMR (80 MHz, C 6  D 6 ) δ (ppm) : 23.4 (s).