CA2024284A1 - Carbonylation of methanol using a novel transition metal catalyst precursor - Google Patents

Abstract

"CARBONYLATION OF METHANOL USING A NOVEL
TRANSITION METAL CATALYST PRECURSOR"

ABSTRACT OF THE DISCLOSURE

An improved process is provided for the carbonylation of methanol to acetic acid and/or its derivatives, especially methyl acetate, under mild reaction conditions using a novel catalyst precursor. The precursor is a transition metal complex having a heterodifunctional phosphorus - nitrogen chelated ligand attached to the metal. The carbonylation reaction can now typically be carried out at 80°C and CO pressure of 40 psig.

Description

2~242g~
FIELD OF THE INVENTION
2 The invention relates ko transition metal catalyst

3 precursors having a phosphorus-nitrogen chelated ligand attached

4 to the metal. It further relates to the use of such precursors in the carbonylation of methanol, typically to produce methyl 6 acetate.

8 The homologation, hydroformylation and carbonylation 9 reactions of methanol to produce carbon oxygenates are well documented.
11 The homologation reaction is exemplified by the 12 reaction of methanol with synthesis gas (a mixture of carbon 13 monoxide and hydrogen) to produce ethanol namely:

14 CH~OH ~ CO ~ H2 ~c2HsoH

The reaction typically is conducted in the presence of 16 a Co-Ru-I catalyst, at elevated temperatures and pressures (up 17 to 10,000 p.s.i.g.).
18 However, in U.S. Patent 4,727,200 there is disclosed 19 an alcohol homologation reaation wherein methanol is reacted with synthesis gas in contact with a rhodium/ruthenium, iodine, 21 diphosphine catalyst system.
22 The hydroformylation (or reductive carbonylation) 23 reaction is exemplified by the reaction of methanol with 24 synthesis ga~ to form acetaldehyde:

CH30H + CO + H2 ~ CH3CHO

2 ~ ~

1 Typically, a Co-I or Rh-I-PR3 catalyst i6 utilized, 2 again at elevated temperatures and pressures.
3 Tertiary polyphosphine monoxide ligands are used in the 4 hydrofor~ulation processes described in the following patents:
Rl f 6 U.S. Patent 4,429,161: P - Y - P ~ R3 8 Ar O
9 U.S. Patent 4,400,548 / PY - P - Rl ; and U.S. Patent 4,522,933 Ar R2 11 Ar p 12 U.S. Patent 4,593,011 \ PY - P R2 13 U.S. Patent 4,491,675 Rl R3 14 Additionally, the use of phosphite ligands in hydroformulation processes is taught in the followings patents:

16 U.S. Patent 4,599,206 C-17 U.S. Patent 4,717,775 ~ \
18 U.S. Patent 4,737,588 5 , P - o - w 19 U.S. Patent 4,789,753 ~ /
~ o 21 U.S. Patent 4,668,651 O
22 U.S. Patent 4,769,498 ~ \
23 ~ / ~ -X ; and 24 0 m ' :
.

2~2~
1 U.S. Patent 4,748,261 ~ O O - Z
2 ~ P- O- W- O-P

4 Further hydroformylation processes using sulphonated tertiary phosphine ligands are described in U.S. Patents 6 4,716,250 and 4,731,486.
7 The carbonylation reaction is exemplified by the 8 reaction of methanol with carbon monoxide to form aaetic acid or 9 methyl acetate, depending on the solvent used.
(H20) 11 CH3OH + CO ~CH3COOH

13 (CH30H) P
14 2CH3OH ~ CO - > CH3-C-O-CH3~H2O
In U.S. Patent 3,769,329, issued to F.E. Paulik et. al.
16 there is disclosed a carbonylation process which comprises 17 reacting methanol with carbon monoxide at 175C and 1000 p.s.i.g.
18 to form acetic acid. This process is illustrative of existing 19 industrial conditions for conducting the reaction.
U.S. Patent 4,670,570, issued to Wegman et. al. details 21 a process for the production of carboxylic acids from alcohols 22 using rhodium complex catalysts.
23 More specifically, the catalyst comprises:

24 Rh(Co)X(RIRlPGZ) wherein 26 Z is selected from the group consisting of:

27 -PR'R' ; -COR'' ; or -CR'' 2~ O O O

2 ~ ~

1 and G represents the two 2 R' ~R'l and 3 .. _ f_ lt tct c-c - -c- _ 4 R ' "1 a ~R ',~ b R' b S The Wegman reaction conditions ar~ mild, typiaally 6 involving reaction temperatures less than about 130C and a 7 reaction pressure less than about 250 p.s.i.g.

9 In accordance with one aspect of the present invention, there is provided a novel transition metal catalyst precursor 11 having a phosphorus nitrogen chelated ligand attached to the 12 metal.
13 Preferably the metal is selected from the transition 14 metal sub-group consisting of Rh, Ni and Co.
Preferably, the chelated ligand comprises a 16 substantially unreactive connecting backbone structure of two or 17 more atoms. More preferably, the connecting backbone structure 18 comprises saturated hydrocarbon entities (CH2)n, wherein n = 1 or 19 2, attached to a pentavalent phosphorus which in turn supports the nitrogen as an iminatophosphorane. Alternatively, the 21 oonneoting backbone structure comprises a benzene ring 22 substltuted in ad~acent positions by a substituted phosphine and 23 a substituted iminatophosphorane.
:`
:24 There i8 provided a transition metal complex catalyst precursor having the general ~ormula I given below:

.

.~ :
,:;

.
~' 2~2~2~
Ph2 3 / ~ ~
4 (H2C)n M (I) Ph2P ~ z 6 ~ N

8 wherein 9 M is a transition metal, preferably Rh, Ni or Co, A B Cl 11 R = CO~E or SiMe3 or Ti - Cl or no sub6tituent, 12 C D Cp l3 and wherein 14 Ph is a phenyl group, Me i8 a methyl group, 16 A, B, C or D are selected from F or H
l7 or N02 or an alkyl group l8 or an aryl group, l9 E is endocyclic nitrogen or a C-CN group or 1somsrs thereof, Cp:is cyclopentadiene 21 X is P or As, and 22 n i6 1 or 2.
23 The combination o~ the speci~io elements in -the 24 cataly~t preaursor results in an efficacious catalyst system which ha~ been~ound to be active under mild conditions ~or 26 cata1ysis of the carbonylation of methanol to acetic acid and 27 its esters.
, ~ :

2 ~
1 Without being bound by the following, it is believed 2 that the heterodifunctional character of the phosphorus-nitrogen 3 ligand provides a chelate complex in which the unequal binding 4 of the phosphorus and the nitrogen to the metal results in the preferential dissociation of the more weakly bound coordinating 6 atom, so as to provide a reactive site at the metal. The 7 unreactive backbone of the ligand keeps the dissoclated element 8 readily available for recombination, so as to facilitate the 9 cyclical nature of the catalytic process. Thus in the case of the Rh(I) complex, catalytic oarbonylation of methanol to acetic 11 acid and/or its esters proceeds under mild conditions of 12 temperature and pressure because the facile dissociation of 13 nitrogen appears to allow coordination of molecular CO to the 14 rhodium centre to form the reactive species.
In the specific case of Rh(I) catalysis, it is believed 16 that the Rh(I) oentre is oxidatively converted to a Rh(III) 17 complex and that the adduct provides the vehicle ~or catalytic 18 transformation. Dissociation of the nitrogen substituent and 19 coordination of free CO in this case forms a complex which appears to subsequently suffer internal rearrangement to an acyl 21 substituted Rh complex. Upon removal of the acyl substituent, 22 the uncoordinated nitrogen, held to -the metal by the coordinatPd 23 phosphorus and the backbone structure of the ligand molecule, is 2~ in a suitable positlon to coordinate to the Rh centre and stabilize the catalytic unit so that the cyole may be continued.
26 In a sacond broad aspect of the invention it has been 27 discovered that when the above--described Rh complexes are 28 utilized as catalysts in the known carbonylation reaction of 29 methanol, ~hen the reaction w~ll take place under very much ~2~2~
1 milder conditions than had heretofore been reported. More 2 specifically, the reaction may be conducted at a temperaturs o~
3 about 80C and CO pressure of about 40 p.s.i.g.
4 Without being bound by same it is believed that because of the placement of an ~ctivated R-substituent, in particular a 6 fluoroaromatic compound, it is possible to ~fine tune~ the 7 catalyst so as to selectively control the carbonylation reaction.
8 In another aspect of the invention, it has been 9 discovered that the carbonylation of methanol with carbon monoxide can further be promoted using a promoter that enhances 11 the o~idative addition of methyl iodide to the metal cen~re, 12 thereby accelerating the reaction. Examples of such promotors 13 are lithium acetate, sodium tetraphenyl borate, and Bezman salt 14 having the formula 16 Ph2P ~ PPh2 Cl 18 Broadly stated then, in a catalyst aspect, the 19 invention co~prises a transition metal catalyst precursor having a phosphorus-nitrogen chelated ligand attached to the metal.
21 Broadly stated, in a process aspect the invention is 22 an improvement in a catalytic process for carbonylation o~
23 methanol to acetic acid and/or its esters. The improvement 24 comprises reacting the methanol and carbon monoxide using a transition métal catalyst precursor having a phosphorus-nitrogen 26 chelated ligand attached to the metal as a catalyst.

-` 2~2~2~

2 In accordance with the best mode of the present 3 invention, a process is provided which uses a novel rhodium 4 complex catalyst precursor for the carbonylation reaction of methanol to form methylacetate. However Ni and Co have also been 6 shown to work. In using the catalyst precursor it is possible 7 to conduct the carbonylation reaction under particu}arly mild and 8 hence more energy efficient conditions.
9 The reaction conditions for carrying out the carbonylation process of this invention can be those heretofore 11 conventionally used and may comprise a reaction temperature from 12 about 25C to 200C and pre6sure from about 1 to 5000 p.s.i.g.
13 However the preferred carbonylation process will be that which 14 is most efficient in producing methyl acetate and/or acetic acid from CH30H. The optimization of the reaction conditions needed 16 to achieve the best conversion, efficiency and catalyst life will 17 be within the knowledge of one skilled in the art and easily 18 assessed by following the preferred embodiments of this invention 19 as deccribed in dstail below or in the experimental section.
As stated, the reaction temperature may range between 21 25C and 200C. The preferred temperature is in the range between 22 80C to 120C. The CO pressure will range from 1 p.s.i.g. to 23 5,000 p.s.i.g. The preferred pressure i6 betwee~ 40 to 400 24 p.s.i.g. The reaction time will ran~e from 30 minutes to 6 hours.
26 The llgands employable are thosa havlng the general 27 formula II or III:

2~2~2~

~. (CH2)\ (CH2)n 2 Ph2X IlPh2 llh2P IlPh2 II III

6 wherein the substituents are as previously defined.
7 Illustrative examples of the bifunctional ligands 8 employable in this invention include:
9 / CH2 ~
Ph2P PPh2 12 SiMe3 : 13 ,~CH2 14 Ph2P PPh2 N
16 ~ O ~
17 ~ F

19 ~CH2)2 Ph2P IPlPh2 22 SiMe3 ;~: :
'' , , . 10 , , 2 ~ 2 ~ ~

(CH2)2 2 Ph2P / PPh2 Il 4 F~F
F~/ F

8 Ph2P IPl Ph2 ~ N02 ` 11 2 12 . CH2 13 Ph2P PPh2 F~F
~`~ 17 N
.

8 ~ ~ ~CH2)2 j 19 Ph2AS llPh2 N
.~ 21 SiMe3 : ~ .
'~ :
,~ 11 :, , --" 2~2~2~
,~\
2 Ph2P IPlPh2 3 S iMe3 Ph2P ll Ph2 7 O-- P=. O
8 OPh Ph P''/ ~ PPh2 : 2 1l . ~ 11 N
12 ~ F ~l--CN
13 : CN~ ` F

3 :: 14 ~ F

: ~ : 15 ~ . CH2 ~i 6 ~ Ph2PIl IPlPh2 :17 N N
18 SlMe3 SiMe3 :
. , , I

, ~
,i , 2~2~2~

~ (CH2)2 ~h2P IlPh2 4 F~F F~F

' <~
7 Ph2P ll Ph2 '.. : 8 N

F ~ F

12 and the like.
13 In the conversion react~on it is to be noted that an " :

14 excess of ligand is used. It is possible that the excess ligand can be the heterodifunctional ligand or a suitable phosphine, 16 such a triphenylphosphine. It has been observed that the use 17 of excess heterodlfunctional ligand provides better turnover 18 numbars compared to when a phosphine i8 used a the excess : : : :
19~ ligand, proving the superiority of the difunctional ligands.
To effect the conversion of methanol to methyl acetate 21 the catalytic precursor can be added to the system either in the ~ 22 ~orm of a metal complex prepared by the procedures described in ;~ 23 detail in the experimental section or can be added as the 24 transition metal precursor and the ligand, thus preparing the ; 25 complex in-situ. The Rh metal can be added in any of several , :

~::

. .

2~2~2~

1 forms including [Rh(CO)2)Cl]2, [Rh(Cod)Cl]2 and the Co and Ni in 2 the form of acetates or as other suitable salts.
3 Most of the reactions have been carried out using 4 methanol itself as the solvent. However other solvents like methyl acetate, which is the product from the carbonylation of 6 methanol, acetophsnone or similar solvents can be employed for 7 carrying out the reaction.
8 Under the reaction conditions employed, lower 9 concentrations of the catalyst provide higher turnover numbers.
However adjustment of the reaation conditions should yield higher 11 turnover numbers and good reaction rates at higher concentrations 12 of the catalyst. The concentration may range from 25 to 2,000 13 ppm transition metal and more preferably from about 50 to 1,000 14 ppm calculated as free metal.
The following examples are illustrative of the present 16 invention and are not to be regarded as limitative.

18 All experimental manipulations were per~ormed under an 19 atmosphere of dry argon. Solvants were dried and distilled prior to use. Bis(diphenylphosphino)methane (dppm), 1-21 diphenylphosphino-2-diphenylarsinoethane (ARPHOS), and Me3SiN3 22 were commercial materlals obtained from Aldrich. Compound IV was 23 prepared as previou~ly described in Inorg. Chem. 1989, 28, 413 24 by Katti, K. V. and Cavell, R.G.
~ ~2C \
26 Ph2ll PPh2 28 SiMe3 IV
~:

2~2~.~2~

; 1 IH, 19F, 31p, and 29Si NMR spectra were obtained on a 2 Bruker WH 400 instrument (operating at 400.13, 376.40, 161.97, 3 and 79.50 MH2, respectively) using SiMe4, CFCl3, 85% H3PO4, and 4 SiMe4, respectively, as the external ~tandards. An INEPT
sequence was employed to enhance signal~ in the 29Si NMR
6 spectra. 20 In all the spectroscopic studies CDCl3 was used as 7 both the solvent and the internal lock. Positive shifts lie 8 downfield of the standard in all cases. Solution molecular 9 weight measurements were performed in dibromomethane solution with a Mechrolab 30lA vapor phase osmometer.

11 Example I
12 Synth~sis o~ p-(N-C)C6~4N=PPh2CH2PPhz (V). To a solution o~ IV
13 (5.123 g) 10.80 m moles) in dry toluene (100 mL) was injectad 14 pentafluorobenzonitrile (3.126 g, 16.20 m moles) by using a syringe. ~he reaction mixture was refluxed for 12 h before the 16 solvent was removed in vacuo to leave a pale yellow Bolid. The 17 crude product V was crystallized .+rom acetonitrile to obtain a 18 pure compound (yield 5.59 g, 89%; pale yellow needle-shaped 19 crystals; mp 188C). Analysis calculated for C3zH22F4N2P2: C, 67.10; H, 3.84; N, 4.89. Found: C, 67.13; H, 3.81; N, 4.87.
21 MS (EI, m/z): 572 (M+). IH NMR (CDC}3): ~ 7.27, 7.60, 7.85 (m, 22 20 H); PCH2P methylene ~ 3.15 (dd, 2 H, 2JpvH = 12.50V 2JpmH =
1.15 Hz). I9F NMR (CDCl3): AA'BB' spin system ~ -99.85 (m, 2 24 F), -159.25 (m, 2 F).

2B2'.~28~
1 Example 2 2 Syntha~is of p-NCsF4N=PPh2CH2PPh2 (VI). To a solution of IV (4.532 3 g, 9.62 m moles) in dry toluene (100 mL) was injected 4 pentafluoropyridine (2.439 g, 14.40 m moles) by using a syringe.
The reaction mixt~re was refluxed for 20 h before the solvent was 6 removed in vacuo to leave a transparent orange crystalline solid.
7 This crude product was crystallized from acetonitrile to obtain 8 pure VI (yield 4.95 g, 94%; orange cubic crystals; mp 60DC).
9 Analysis calculated for C30H22F4N2P2: C, 65.69; H, 4.01; N, 5.10.
Found: C, 65.66; H, 4.10; N, 5.08. MS (EI, m/z): 548 ~M+). IH
11 NMR (CDCl3): ~7.25, 7.62, 7.87 (m, 20 H); PCH2P methylene 12 3.17 (dd, 2 H, 2JPVH = 12.65, 2JpmH = 1.15 Hz). I9F NMR (CDC13):
13 AA'BB' spin system ~ ~141.43 (m, 2 F), -155.07 (m, 2 F).

14 Example 3 : 15 Synthecl~ o~ p-(N-C)C6F4N=PPh2CH2PPh2~h~CO)Cl (VII). A solution 16 of V (0.145 g, 0.25 m moles) in dry dichloromethane (25 mL) was 17 added dropwise at 25C to a solution of [Rh(CO)2Cl]2 (0.049 g, 18 0.12 m moles) also in the same solvent (25 mL). The mixture was 19 stirred at the same temperature for 4 h before the solvent was removed i~ vacuo to yield an analytically pure brown crystalline 21 solid of VII as a dichloromethane solvate (yield, after washing 22 with hexane (5 mL), 0.18 g, 90~; brown mlcrocrystalline; mp 23 215C dec). Analysis calculated for C34H24Cl3F4N2OP2Rh: C, 49.55;
24 H, 2.91; N, 3.40; Cl, 12.91. Found: C, 49.53; H, 2.89; N, 3.38;
Cl, 12.90. IH NMR (CDCl3): phenyl rings ~ 7.27, 7.65, 7.90 (m, `~ 26 20 H); PCH2P methylene ~ 3.78 (dd, 2 H, 2J~Ip = 12.0, 8.20 Hz).
27 19F NMR (CDCl3): AA'BB' spin system ~-137.27 (m, 2 F), -142.56 28 (m, 2 F).

'~

', ;~:

2~2'~2~

1 Example 4 2 Syntha~i~ of p-NCsH4N=PPh2CH2PPh2~h(CO)Cl (V~II). The reaction of 3 VI with [Rh(CO)2Cl]2 was carried out under similar experimental 4 conditions to those described for VII to obtain the dichloromethane solvate of VIII in 88% yield (yellow 6 microcrystalline; mp 180C dec). Analysis calculated for 7 C32H2~Cl3F4N2OP2Rh: C, 48.04; H, 1.25; N, 3.50. Found: C, 48.11;
8 H, 1.21; N, 3.47. IH NMR tCDCl3): pherlyl rings ~ 7.26, 7.60, 9 7.88 (m, 20 H); PCH2P methylene ~ 3.75 (dd, 2 H, 2JHP = 12.10, 7.50 Hz). I9F NMR ~CDCl3): AA'BB' spin system ~ 138.15 (m, 2 11 F), -147.50 (m, 2 F) .

12 ~xample S
Synthesi~ o~ Me3$iN=PPh2(CH2)2AsPh2 (IX). A solution of Me3SiN3 14 (2.25 g, 19.64 m moles) in toluene (25 mL) was added dropwise at room tempera~ure to a solution of Ph2P(CH2)2AsPh2 (ARPHOS) (7.55 16 g, 17.08 m moles) also in toluene (100 mL). The mixture was 17 heated under reflux for 16 h befor~s the so1vent was removed in 18 vaauo to yield an off-white crystalline solid which was 19 recrystallized from dry acetonitri1e to obtain pure IX (yield 8.75 g, 96%; mp 131C). Analysis calculated for C29H33NAsPSi: C, 21 65.79; H, 6.23; N, 2.64. Found: C, 65.76; H, 6.19; N, 2.63.
22 MS(EI,m/z): 5.28 (M~). 31p NMR (161.93 MHz in CDCl3, vs 85%
23 H3PO4): ~ 1.û3 ppm. 29si NMR (INEPT; 79.5 MHz in CDCl3, vs 24 Me~S1): ~ -11.33 (d, 2J(29Si-3lP) = 19.57 Hz).
;

2~2~2~
1 Example 6 2 Synthe~ls o~ Arsenic Complexe0 and Compounds.
3 (a). Me3SiN=PPh2(CH2)2A~Ph2Rh(CO)Cl (X). A solution of IX (0.310 4 g, 0.58 m moles) in dry dichloromethane (50 mL) was added

5 dropwise (20 min~ to a solution of [Rh(CO)2Cl~2 (0.113 g, 0.29 m

6 moles) al~o in the same solvent. The reaction mixture was

7 stirred at 25C for 2 h before the solvent was removed in vacuo

8 to yield an analytically pure dichloromethane solvate of X

9 (yield, after washing with hexane (5 mL), 0.43 g, 95%; yellow microcrystalline; mp 165C dec). Analysis calculated for 11 C31H3sCl3NOAsPRhSi: C, 47.68; H, 4.48; M, 1.79; Cl, 13.63. Found:
12 C, 47.65; H, 4.46; N, 1.77; Cl, 13.60. IH NMR (CDCl3): phenyl 13 rings ~ 7.35, 7.55, 7.70 (m, 20 H); AsCH2CH2P ~ 2.17 (m, 2 H), 14 2.60 (m, 2 H); Si(CH3)3 ~ 0.05 (s, 9 H). 29Si NMR (INEPT; CDCl3):
~ 6.20 (a, 1 Si, 2Jpvsl, = 5.50 Hz).

16 (b)- ~he Metallaoyale~ N=PPh2(CH2)2A~PhzRh(cod) tXI) and .
17 N=pEh2tcH2)2A9ph2Ir(aod) ~XII) were prepared by employing similar 18 experimental conditions to those described above for X.
; XI CH2Cl2: yield 82%; yellow microcrystalline; mp 170C
dec. Analysis calculated for C3sH38Cl2NAsPRh: C, 55.87; H, 5.05;
;~21 N, 1.86; Cl, 9.43. Found: C, 55.85; H, 5.01; N, 1.84; Cl, 9.49.
22IH NMR (CDCl3j phenyl rings ô 7.37, 7.60, 7.80 (m, 20 H);
23A8CH2CH2P ~ 2. 25 (m, 2 H), ~ 2.65 (m, 2 H); aod olefinic ~ 5. 30 24(br, 2 H), 5.45 (br, 2H); cod methylene ~ 2.30 (br, 4 H~, 1.70 (br, 4 H).
26XII CH2Cl2:yield 85%; brown microcrystalline; mp 27190C dec.Analysis calculated for C3sH3gCl2NAsPIr: C, 49.93; H, 28 4.52; U, 1.66; C1, 8.43. Found C, ~0.01~ H, 4.49; N, 1.65; C1, ' ~242~
1 8.46. IH NMR (CDCl3): phenyl rings ~ 7.35, 7.62, 7.85 (m, 20 2 H; AsCH2CH2P ~ 2.19 (m, 2 H), 2.60 (m, 2 H); cod olefinic 3 5.32 (br, 2 H), 5.40 (br~ 2 H); cod methylene ~ 2.30 (br, 4 H), 4 1.72 (br, 4 H).

Exampl~s 7 & 8 6 0.0308 g of [Rh(C0)2Cl]2 (0.079 m moles) was dissolved 7 in 5 ml of methanol in a 50 ml pop bottle reactor maintained 8 under an argon atmosphere. To the stirred solution 0.0812 g of 9 the difunctional ligand Ph2P-(CH2)2-Ph2P=N-SiMe3 (0.140 m moles) was addsd. The mixture was stirred for 10 minutes. Then 0.2138 11 g o~ Ph3P (0.82 m moles) was added followed by 0.4118 g of 12 lithium acetats (4.0 m moles), 1 ml of CH3I (15 m moles) and 13 finally 5 ml of methanol. Then the tube was flushed with carbon 14 monoxide and sealed. The reactor was then placed in an oil bath maintained at 80-85C and pressurized with CO to 40 p.s.i.g. The 16 reaction was followed by taking samples at detexmined intervals 17 of time by momsntarily stopping the reaction and removing a 18 sample with a syringe.
19 In Table I data is presented for the run along with the data for a similar run with no Ph3P added. The rates were 21 determined by measuring the amount of methylacetate formed during 22 the run using gas chromatograph.
23 T~BLE I
24 Ex. No. Rh/Ligand/Ph3P Ratio Reaction Rate 1 1:2:10 2.0 g moles/l/hr.
26 2 1:10:0 2.5 g moles/l/hr.
:

,~:
.;
:

2~2~g~

1 When the difunctional ligand is used as the excess 2 ligand the reaction rate is higher, even though the total 3 Rh:Ligand ratio is lower.

4 Example 9 0.0124 g of [Rh(CO)2)Cl]2 (0.032 m moles) was dissolved 6 in 5 ml of methanol in a 50 ml pop bottle reactor maintained 7 under an argon atmosphere. To the stirred solution 0.134 g of 9 the difunctional ligand Ph2P-CH2-Ph2=N ~ ~ -CN
'F F
11 (0.234 m moles) was added. The mixture was stirred for 10 12 minutes. Then 0.244 g of lithium acetate t2.4 m moles), 1 ml of 13 CH3I (16 m moles) and finally 5 ml of methanol were added. Then 14 the tube was flushed with carbon monoxide and sealed. The reactor was then placed in an oil bath maintained at 90-94C and 16 pressurized with cn to 40 p.s.i.g. rrhe reaction was followed by 17 taking samples at determined intervals of time by momentarily 18 stopping the reaction and removing a sample with a syringe.
19 In Table II data is presented or the run.
TABLE II
21 Ex. No. Rh/Ligand Molar Ratio Reaction Rate 22 3 1:7 1.2 g moles/l/hr.
.
23 Ex~m~le 10 24 0.0130 g of [Rh(CO)2]z t0.033 m moles) was dissolved in 5 ml of methyl acetate in a 50 ml pop bottle reaator maintained ~6 under an argon atmosphere. rTo the stirred solution of 0.1348 g 28 o~ the difunctional ligand Ph2P-CH2-Ph2P=N _ ~ - CN
29 ~ F
(0.236 m moles) was added. rrhe mixture was stirred for 10 31 minutes. Then 0.213 g of lithium acetate (2.1 m moles), 1 ml o~

;~ . 20 .

; :
.
.
~: :

2~2~
1 CH3I (16 m moles) and 5 ml of methanol were added. The tube was 2 flushed with carbon monoxide and sealed. The reactor was then 3 placed in an oil bath maintained at 84-90C and pressurized with 4 CO to 40 p.s.i.g. The reaction was followed by taking samples at determined intervals of time by momentarily stopping the 6 reaction and removing a sample with a syringe.
7 Data for the run is presented in Table III:

9 Ex. No. Rh/Ligand molar ratio Reaction Rate 4 1:7 0.6 g moles/l/hr.
11 Comparing the rate to example number 3, changing 12 solvent to methyl acetate seems to lower the reaction rate under 13 the experimental conditions employed.

.
14 Example lL
A series of runs were aarried out using [Rh(CO)2Cl]2 16 as the metal source, Ph2P-(CH2)2-PH=N-SiMe3 as the ligand and Ph3P
17 as the excess ligand, employing conditions as described in 18 examples 7 and 8.
19 ~he results obtained are presented in ~able IV:

::`

~2~2~l~

2Turnover Number* As a Function of the Moles 3Of Rhodium Compound 4 R`nodium Compound** Turnover Number 0.026 x 10'3 moles 730 6 0.097 x 10'3 moles 223 7 0.145 x 10'3 moles 200 8 0.168 x 103 moles 125 9 O.l95 x 103 moles 95 * measured for the reaction of methanol with carbon monoxide 11in the presence of lRh(CO)2Cl]2(x m mole6) ~ Ph2-CH2-CH2-12PPh2=NSiMe3(2 ~ m moles) + Ph3P (0.77 m moles) + Lithi.um 13acstate (4 m moles) 14 ** as monomeric species in solution 15The data indicate that for lower concentration of the 16 catalyst, the turnover numbers are higher under the experimental 17 conditions employed.

18 Exampl 12 l90.1444 g of cobalt acetate tetra hydrate (0.6 m mole) was added to 5 ml of methanol in a 50 ml pop bottle reactor 21 maintained under an argon atmosphers. To the stirred ~olution 220.4l84 g of the difunctional ligand Me3Si-N=PPh2-CH2-CH2-PPh2=N-23 SiMe3 (0.73 m mole) was added. The mixture was stirred for lO
24minutes. Then 0.2034 g of Ph3P (0.78 m mole) 0.4244 g of lithium 25acetate (4.2 m mole), l ml of CH31 (16 m moles) and 5 ml of 26 methanol were added. The tube was flushed with carbon monoxide :
.

,~`

2 ~ 2 ~
1 and 6ealed. The reactor was then placed in an oil bath 2 maintained at 84 - 90nC and pressurized with CO to 40 p.s.i.g.
3 At the end of 20 hours the reaction mixture contained 5% of 4 CH3COOCH3, indicating a lower catalytic activity by the cobalt complex, compared to the Rh complex.

6 Example 13 7 0.1454 g of nickel acetate tetra hydrate (0.6 m mole) 8 was added to 5 ml of methanol in a 50 ml pop bottle reactor 9 maintained under an argon atmosphere. ~o the stirred solution 0.4530 g of the difunctional ligand Me3Si-N=PPh2-CH2-CH2-PPh2=N-11 SiMe3 ~0.79 m mole) was added. The mixture was stirred for 10 12 minutes. Then 0.1~84 g Ph3P (0.76 m mole), 0.4672 g of lithium 13 acetate, 1 ml of CH3I (16 m mole) and 5 ml of methanol were 14 added. The tube was flushed with carbon monoxide and sealed.
The reactor was then placed in an oil bath maintained at 84 -16 90~C and pre~surized with CO to 40 p.s.i.g. At the end of 20 17 hours the reaction mixture contained 5.9% of CH3COOCH3, indicating 18 a lower catalytic activity by the nickel complex compared to the 19 Rh complex.

Exam~le 14 21 0.0300 g of [Rh(CO)2Cl]2 (0.08 m mole) was adcled to 5 22 ml of methanol in a 50 ml pop bottle reactor maintained under an 23 argon atmosphere. To the stirred solution 0.2538 g of the difunctional ligand Ph2P-CH2-PPh2=N ~ CN (0.44 m mole) 27 was added. The mixture was stirred for 10 minutes. Then 1.0248 28 g of the promotor Ph2P - N PPh2 Cl (2.3 m mole), 1 ml of 29 NH2 ~ NH2 . ~ ~

~: .
.

2~2~

1 of CH3I (16 m mole) and 5 mls of methanol were added. The tube 2 was flushed with carbon monoxide and sealed. The reaator was 3 then placed in an oil bath maintained at 84 -- 90C and 4 pressurized to 40 p.s.i.g. with CO. The reaction rate was measured by monitoring the concentration of the methyl acetate 6 formed during the run. The initial rate of formation of methyl 7 acetate was found to be 0.9 g moles/l/hr.

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Claims (19)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A transition metal catalyst precursor having a phosphorus-nitrogen chelated ligand attached to the metal.

2. The precursor of claim 1 wherein the transition metal is rhodium.

3. The precursor of claim 1 wherein the transition metal is nickel.

4. The precursor of claim 1 wherein the transition metal is cobalt.

5. In a catalytic process for carbonylation of methanol to acetic acid and/or its esters, the improvement comprising:
reacting the methanol and carbon monoxide using a transition metal catalyst precursor having a phosphorus-nitrogen chelated ligand attached to the metal as a catalyst.

6. The improved process as set forth in claim 5 wherein the metal is Rh.

7. The improved process as set forth in claim 5 wherein the metal is Ni.

8. The improved process as set forth in claim 5 wherein the metal is Co.

9. The precursor as set forth in claim 1 wherein the chelated ligand comprises a connecting backbone structure of two or more atoms, which structure is substantially unreactive.

10. The precursor as set forth in claim 1 wherein the connecting backbone structure comprises saturated hydrocarbon entities (CH2)n where n=1,2 attached to a pentavalent phosphorus which in turn supports the nitrogen as an iminatophosphorane.

11. The precursor as set forth in claim 9 wherein the connecting backbone structure comprises a benzene ring substituted in adjacent positions by a substituted phosphine and a substituted iminatophosphorane.

12. A transition metal complex catalyst precursor having the general formula I:
(I) wherein M is a transition metal, preferably Rh, Ni or Co, or SiMe3 or or no substituent, and wherein Ph is a phenyl group, Me is a methyl group, A, B, C or n are selected from F or H
or NO2 or an alkyl group or an aryl group, E is endocyclic nitrogen or a C-CN group or isomers thereof, Cp is cyclopentadiene X is P or As, and n is 1 or 2.

13. A process for the carbonylation of methanol to acetic acid and its esters which comprises reacting the methanol and carbon monoxide at a temperature of between about 25 to 200°C
and pressure of about 40-5,000 p.s.i.g. in the presence of a catalyst precursor as set forth in claim 12.

14. A process as described in claim 13 wherein the temperature is in the range of 50 to 120°C and the pressure is in the range 40-400 p.s.i.g.

15. A process as set forth in claim 14 wherein the metal used is Rh, the ligand used is Ph2PCH2CH2PPh2=NSiM3, and lithium acetate is used in the reaction as a promotor.

16. A process for the carbonylation of methanol to acetic acid and its esters which comprises reacting the methanol and carbon monoxide at a temperature of between about 50 to 120°C
and pressure of about 40 - 400 p.s.i.g. in the presence of a catalyst precursor as set forth in claim 1.

17. The process as set forth in claim 16 wherein the transition metal is selected from the group consisting of Rh, Ni and Co.

18. The process as set forth in claim 17 wherein the ligand has the formula II
wherein:

or SiMe3 or or no substituent,

19. The process as set forth in claim 17 wherein the ligand has the formula III

wherein:

or SiMe3 or or no substituent,