CA1257607A - Process for the preparation of urethanes - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process for converting a nitrogen-containing organic compound, selected from the group consisting of nitro, nitroso, azo, and azoxy compounds, into the corresponding urethane, by reacting a solution containing said nitrogen-containing organic compound and a hydroxyl-containing organic compound with carbon monoxide, in the presence of a ruthenium catalyst comprising a bis-phosphine ligand, at conditions sufficient to convert said nitrogen-containing organic compound into the corresponding ureth-ane.

Description

57~7 -1- 27558-lD

This application is a divisional of application No. 463,144 filed on September 14, 1984.
The inv.entions.. of the parent and divisional applicatiPn$
relate to a process for preparing urethanes by reacting a solution of a nitrogen-containing organic compound and a hydroxyl-containing organic compound with carbon monoxide in the presence of a ruthenium catalyst. In the parent application the catalyst comprises a halide-free ruthenium compound and in the divisional application the catalyst comprises a ruthenium compound comprising a bis-phosphine ligand.
Isocyanates such as toluene diisocyanate (TDI) and 4,4'-diisocyanato diphenyl methane (MDI) are used commercially in the preparation of urethane polymers. The present commercial technology for the preparation of these isocyanates utilizes phosgene, which is costly, toxic, corrosive, and difficult to handle. It is thus understandable that a great deal of recent research has been directed toward different methods for preparing isocyanates, especially TDI and MDI.
Various patents have disclosed methods for carbonylat-ing nitrogen-containing organic compounds, e.g. nitro compounds, amines, azo-and azoxy compounds to either isocyanates or urethanes in the presence of a platinum group metal-containing catalyst;
usually a palladium or rhodium-containlng catalyst, and most often a palladium halide-containing catalyst. (The urethanes can be decomposed to yield the corresponding isocyanates).

~L~5~)'7 -la- 27558-lD

Generally, a cocatalyst (promoter) or a coreactant has been utilized in combination with the aforementioned platinum group metal-containing ca-talysts; Lewis acids, Lewis bases, oxidizing agents, reducing agents, etc. have been used as cocatalysts or coreactants in the platinum group metal-catalyzed carbonylation of nitrogen-containing organic compounds. It is important to note that the vast majority of the research on the carbonylation of nitrogen-containing organic compounds has been directed to catalysis by rhodium or palladium-containing catalysts; espec-ially palladium halide-containing catalysts. Therefore the cocatalysts or coreactants, that have been disclosed, have a demonstrable effect on the activity and selectivity of a palladium-containing catalyst; but the effect of such ~l~5~

- 2 - 27558-lD
cocatalysts on the activity or selectivity of other platinum group metals or compounds is speculative.
Due to the complex nature of catalysis, it is o-ften difficult to predict the effect of a known cocatalyst or coreact-ant on a catalyst having a different metal as the catalytically active moiety. Therefore, although U. S. Patent 4,178,455 dis-closes that the reaction rate and yield (in a platinum group meta]
catalyzed process for preparing an aromatic urethane) is increased by a promoter consisting of a Lewis acid (e.g. metal halides, and especially iron chlorides) and an organic primary amino compound, a urea compound, a biuret compound, an allophanate compound, or a mixture thereof, it is not obvious that such promoter is effective either in the absence of the Lewis acid or with a platinum group metal or platinum group metal compound other than palladium or palladium chloride. As a result, the effect of the promoter, disclosed in U. S. Patent 4,178,455 on o-ther catalyst metals can not be predicted with a reasonable degree of certainty.
In the few references which suggest that ru-thenium compounds are suitable catalysts for the carbonylation of nitrogen--containing organic compounds to the corresponding ure-thanes or isocyanates, the catalyst is either a ruthenium halide, or a halide-containing moiety is combined with the ruthenium com-pound to provide the active catalyst. For example, in U. S.
Patents 3,660,458; 4,134,880; and 4,186,269; the ruthenium com-pound that has demonstrated catalytic activity is ruthenium chlor-ide. In U. S. Patent 3,461,149 and 3,979,427 ruthenium-on-alumina ~57~;0~

- 3 - 27558-lD
is treated with halide-containiny compounds, such as ferric chloride or 1,1,2-trichloro - 1,2,2,-trifluoroethane, to provide a heterogeneous catalyst.
Another example of a heterogeneous ruthenium catalyst for the preparation of aromatic isocyanates may be found in U.S.
Patent 3,737,445. This patent discloses a gas-phase process for reacting carbon monoxide with an aromatic nitro or nitroso compound to yield an aroma-tic isocyanate.
It is also well known that the ligand or anion associated with a platinum group metal will vary the catalytic properties thereof. In a process for manufacturing urethanes from alcohols and phenols, carbon monoxide and nitro compounds, in the presence of a catalyst comprising a transition metal complex, as disclosed in U. S Patent 3,448,140, the presence of a chelating bis phosphino moiety increases the yield of iridium-containing complexes and decreases the yield of rhodium-con-taining complexes.
(Compare Example Nos. 1 and 2 with Example Nos. 4 and 5).
Therefore, although the combination of a phosphine ligand wi-th a platinum group metal catalyst moiety is suggested in U. S. Patents 20 3,454,620; 3,523,962; and 3,993,685 (as well as U. S. Patent 3,448,140); there is no basis for predicting the behavior of a catalyst comprising the combination of phosphine ligands and a ruthenium moiety, from the demonstrated catalytic behavior of phosphine ligands in combination with other platinum group metal compounds.
~uthenium compounds have been utilized in the reduction of organic nitro compounds to the corresponding amines with mix-- 3a - 27558-lD
tures of hydrogen and carbon monoxide. It was reported in U.S.
3,729,512 that the reduction of -the organic nitro compound with carbon monoxide and ethanol, in -the absence of H2, resulted in a mixture of amine and a urethane. The patentee was not concerned with the preparation of a urethane product; therefore, there was no attempt to increase the selectivity above the approximately 22 percent, urethane, that was obtained.

~ 7~7 27558-1 ..
Briefly, the invention of the parent application provides an improved process for converting a nitrogen-containing organic compound, selected from the group consisting of nitro, nitroso, azo and azoxy compounds, into the corresponding urethane by reacting a solution, comprising said nitrogen-containing organic compound and a hydroxyl containing organic compound, with carbon monoxide, which comprises the steps of: (a) providing a primary amine in said solution, and (b) reacting the solution of step (a) with carbon monoxide in the presence of a catalyst comprising a halide-free ruthenium compound, at condi-tions sufficient to con-vert the nitrogen-containing organic compound to the.corresponding urethane.
The invention of the dlvisional application provides a process for converting a nitrogen-containing organic compound, selected from the group consisting of nitro, nitroso, azo~d azoxy compounds, into the corresponding urethane~ by reacting a solution containing said nitrogen-containing organic compound and a hydroxyl-containing organic compound with carbon monoxide in the presence of a ruthenium catalyst comprising a bis-phosphine ligand at conditions sufficient to convert said nitrogen-containing organic compound into the corresponding urethane.
While not wishing to be bound by theory, it appears that, in the ruthenium catalyzed carbonylation of the above nitrogen-containing organic compound to the corresponding urethane, the nitrogen-containing organic compound must first be reduced to a primary amine which then undergoes oxidative carbonylation to the urethane. These reactions which are illustrated below (wherein ~H]

~ 5~
-5- 27558~1 represents the ruthenium hydrogen carrier) must be ef~ectively coupled to provide the desired selectivity to the urethane.
Oxidative carbonylation: C6H5NH2 + CO~CH3 OH `C6H5NHC02CH3+2[H]

Reduction/hydrogenation: C6H5N02 ~ 2C0+2[H] `C6H5NH2+2C02 Net reaction: C6H NO + 3CO+CH OH `C H NHCO CH +2CO

Thus the primary amine (illustrated by aniline) is an intermediate in the formation oE urethane from the nitrogen-containing oryanic compound. It has been found that the halide-free ruthenium compounds used as catalysts in the invention of the parent application are able to efficiently and rapidly reduce the nitrogen-containing organic compounds to the primary amine.
The presence of iron chlorides or similar Lewis Acids is ineffect-ive for increasing the activity of halide-free ruthenium catalysts.
In a carbonylation reaction wherein no primary amine is present, initially, the nitrogen-containing compound (e.g. nitro-benzene) can be reduced to the primary amine (aniline) by added hydrogen or hydrogen equivalents derived from water by the ruthenium-catalyzed water-gas shift reaction. It has been found that the reduc-tion of the nitrogen-containing organic compound to a primary amine in the presence of hydrogen is rapid and provided that the molar ratio of hydrogen -to the nitrogen-containing organic compound is less than 1, the remainder of the nitrogen-containing organic compou~d serves as the oxidant for the oxidative carbonylation of the primary amine to the urethane. Thus, decreasing the molar ratio of hydrogen to the nitrogen-containing organic compound pro-vides urethane in greater selectivity. In the absence of hydrogen, ~5~ 3~ ~
-6- 27558~1 water, or primary amine, the rate of the reaction is very slow as the hydrogen re~uired to reduce the nitrogen-containing organic compound to the primary amine intermediate mus-t be deri~ed by the relatiyely slow oxidation of alcohol. Moreover, the aldehydes which also result from the oxidation o~ alcohol, react wi-th the primary amine to form unwanted condensation products~
The primary amine may also be provided by the in-situ decomposition of a urea or a biuret compound to the corresponding primary amine (s) and urethane in the reaction solution. It has been ~ound that the primary amine substantially increases the rate of conversion o~ the nitrogen-containing organic compound to the corresponding urethane.
Moreover, it has been found that the combination of a halide-free bisphosphine ruthenium catalyst and a primary amine substantially increases the rate of conversion of the nitrogen-containing organic compound to the corresponding urethane and provides a selectivity to urethane o~ 88 percent, or greater, at 100 percent conversion of the nitrogen-containing organic compound.
The nitrogen-containing organic compound will contain at least one non-cyclic group in which a nitrogen atom is directly attached to a single carbon atom and through a double bond to oxygen or another nitrogen atom. The ni.trogen-containing organic compound is selected from the group consisting of nitro, nitroso, azo and azoxy compounds.
Examples of suitable nitrogen containing organic compounds are compounds represen-ted by the general formulae:

-6a~ 76~)~ 2755~-1 I Rl (NOx)y and II Rl-N=N (~)Z R2 wherein Rl and R2 are radicals independently selected from the group consisting of Cl to C20 hydrocarbyl radicals and substituted deriva-tives thereof, x is an integer of from 1 to 2, y is an integer of from 1 to 3, and z is an integer of from O to 1. The substituted hydrocarbyl radical may include hetero atoms selected from the group consisting of halogen, oxygen, sulfur, nitrogen and phosphorous atoms.

~5~ 7 - 7 - 27558-lD
The ni-trogen-containing compounds represented by formula I include nitro compounds (wherein x is 2) and nitroso compounds (wherein x is 1). Suitable nitro compounds are mononitro com-pounds such as nitrobenzene, alkyl and alkoxy nitrobenzenes where-in the alkyl group contains up to 10 carbon atoms, aryl and aryloxy nitrobenzenes, wherein the aryl group is phenyl, -tolyl, naphthyl, xylyl, chlorophenyl, chloronitrobenzenes, aminoni-tro-benzenes, carboalkoxyamino nitrobenzenes wherein the alkoxy group has up to 10 carbon atoms, aryl and aryloxy dinitrobenzenes, trinitro compounds such as trinitrobenzene alkyl and alkoxytrini--tr~benzenes, aryl and aryloxytrinitrobenzenes, -the substituents being any o~ those already mentioned and chlorotrinitrobenzenes as well as similarly substituted mono and polynitro derivatives of the naphthalene diphenyl, diphenylmethane, anthracene and phen-anthrene series. Subs-tituted or unsubstituted aliphatic nitro compounds such as nitrome-thane, nitrobutane, 2,2'-dimethyl nitro-butane, nitrocyclopen-tane, 3-methylnitrobutane, nitrooctadecane, 3-nitropropene-1, phenyl nitromethane, p-bromophenyl nitromethane, p-methoxy phenyl nitromethane, dinitroethane, dinitrohexane, dini-trocyclohexane, di-(ni-trocyclohexyl)-methane are also sui-table.
The above nitro compounds may include more than one of the above substitutents (in addi-tion to the nitro group (s) such as in nitroaminoalkylbenzenes, nitroalkylcarboalkoxyamino benzenes, etc.
From this group of nitro compounds nitrobenzene, nitrotoluene, dinitrobenzene, dinitrotoluene, trinitrobenzene, trinitrotoluene~
mononitronaphythalene, didnitronaphthalene 4,4'-dinitrodiphenyl-methane, ni-trobutane, nitrocyclohexane, p-nitrophenylnitromethane, )7 - 7a - 27558-lD
dinitrocyclohexane, dinitromethylcyclohexane, dinitrocyclohexyl-methane, nitroaminotoluene and nitrocarboalkoxyaminotoluene are pre-ferred and in particular aromatic nitro compounds especially 2,4-and 2,6-dinitrotoluenes, meta and para dinitrobenzenes, and 5-nitro-2-me-thyl-carboalkoxyamino-, -8- 2755~-1 2-nitro-5-methyl-carboalkoxyamino-, and 3-nitro-2-methyl-carboalkoxyamino benzenes.
Examples of suitable nitroso compounds are the aromatic nitroso compounds such as nitrosobenzene, nitrosotoluene, dinitro-sobenzene, dinitrosotoluene and the aliphatic nitroso compounds such as nitrosobutane, nitrosocyclohexane and dinitrosomethylcyclo-hexane.
The nitrogen-containing compounds represented by Formula II include both azo compounds (wherein z is 0) and azoxy compounds (wherein z is 1). Suitable compounds represented by ormula II include azobenzene, nitroazobenzene, chloroazobenzene, alkyl or aryl substituted azobenzene, azoxybenzene, nitroazoxyben-zene, chloroazoxybenzene, etc.
The hydroxy-containing organic compounds include compounds represented by the general formula III Rl (OH)y wherein Rl and y are defined above.
Hydroxy compounds suitable may be, for example, mono- or polyhydric alcohols containing primary, secondary or tertiary hydroxyl groups as well as mono- and polyhydric phenols. Mixtures of these hydroxy compounds may also be used. The alcohols may be aliphatic or aromatic and may bear o-ther substituents in addition to hydroxyl groups but the substituents should (except as here-inafter described) preerably be non-reactive to carbon monoxide under the reaction conditions. Especially suitable compounds are phenol and monohydric alcohols such as methyl, ethyl, n- and sec-propyl, n-, iso, sec- and tert butyl, amyl, hexyl, lauryl, cetyl, \
9 ~ 7~ 27558-1 benzyl, chlorobenzyl and methoxybenzyl alcohols as well as diols such as ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol, triols such as glycerol, trimethylol propane, hexanetriol, tetrols such as pentaerythritol and the ethers of such polyols providing tha-t at least one hydroxyl group remains unetherified. The etherifying group in such ether alcohols normally contains up to 10 carbon atoms and is preferably an alkyl, cycloalkyl or aralykyl group which may be substituted with, for example, a halogen or an alkyl group.
The most preferred hydroxyl~containing organic compound is methyl alcohol or a similar lower alkanol, e.g. a Cl to C5 alcohol.
The processes of the invention of the parent and divis-ional applications includes the use of any mixture of nitro compounds, nitroso compounds, azo or azoxy compounds with any mixture of hydroxy compounds and also the use o~ compounds con-taining both functions, i.e. hydroxynitro compounds, hydroxynitroso compounds, hydroxyazo and hydroxyazoxy compounds such as 2-hydroxynitroethane, 2-hydroxynitrosoethane, nitrophenols, nitronaphthols, nitrosophenols, nitrosonaph-thols, hydroxyazo-benzenes and hydroxyazoxybenzenes. Mixtures of these nitrogen-containing compounds may also be used.
These processes have been found to proceed most smoo-thly to giye -the highest yields when employing nitro compounds. It is accordingly preferred to use nitro compounds rather than nitroso, azo or azoxy compounds.
The primary amine compound utilized may be selec-ted from the group consisting oE compounds represented by the general -10~ 27558~1 ~5~ 37 ~ormula:
Iy Rl (NH2 ) Y
wherein Rl and Y are as defined above. Examples of such primary amines include methylamine, ethylamine, butylamine, hexylamine, ethylenediamine, propylenediamine, butylenediamine, cyclohexylamine, cyclohexyldiamine, aniline, p-toluidine, o-, m- and p-diaminoben-zenes, amino-me-thylcarbanilic acid esters, especially the 5-amino-2-methyl-, 2-amino-5-methyl-, and 3-amino-2-methyl carboalkoxy-aminobenzenes, wherein said alkoxy group has up to 10 carbon atoms, o-, m- and p-nitroanilines, nitroaminotoluenes, especially those designated above, o- and p-phenylenediamine, benzylamine, o-amino-p-xylene, l-aminophthaline, 2,4- and 2,6-diaminotoluenes,

4,4'-diaminodibenzyl, bis (4-aminophenyl) thioether, bis (4-aminophenyl) sulfone, 2,4,6-triaminotoluene, o-, m- and p-chloranilines, p-bromoaniline, l-fluoro-2,4~diaminobenzene, 2,4-diaminophenetole, o,~m- and p-aminoanisoles, ethyl p aminobenzoate, 3-aminophthalic anhydride, etc. These amino compounds may be used alone or in combination.

Among the abo~ve-enumerated amino compounds, those which can be derived from the starting nitro compound are preferred.
For example, when nitrobenzene is used as the starting aromatic nitro compound, aniline is preferred. Similarly, 2-amino-4-nitrotoluene, 4-amino-2-nitrotoluene, and 2,4-diaminotoluene are preferably used when the starting aromatic nitro compound is 2,4-dinitrotoluene, while 2-amino-6-nitrotoluene, and 2,6-diaminotoluene are preferably used when the starting aromatic nitro compound is 2,6-dinitrotoluene.

~ ~5~6~)7 27558~1 The primary amine compound can be provided by the in-situ decomposition of the corresponding urea or biuret as represented by compounds having the general formulae RlNH - I - NHRl.

and RlNH - 11 - N - ~ - NHR
O Rl respectively, wherein Rl is as defined above. Of course, since the above urea and biuret will comprise more than one radical, Rl may represent different radicals in the same compound, that is non-symmetrical ureas and biurets, e.gO

In the invention of the parent application the catalyst utilized comprises a halide-free ruthenium compound~ Unlike other platinum group me-tal-containing catalysts for the carbonylation of nitrogen-containing 6~)~

11 - 27558-lD
organic compounds, the presence of halide in ruthenium catalysts, either as the anion of a ruthenium salt or in a Lewis acid decreases the activity of the ruthenium catalyst. Thus the ruthenium compound may be selected from ruthenium salts, e.g. the nitrate, sulfate, acetate, formate, carbona-te, etc. and ruthenium complexes (especially ruthenium carbonyl complexes) including ligands capable of coordinating with the ru-thenium atom. The complex may include one or more ruthenium atoms and sui-table ligands may include carbon-carbon unsaturated groups as in ethylene, isobutylene, cyclohexene, cyclopentadiene, norborna-diene, cyclooctatetraene. Other suitable ligands include acetyl-acetonate (acac), hydrogen atoms, carbon monoxide, nitric oxide, alkylradicals, alkyl or aryl nitriles or isonitriles, nitrogen-containing heterocyclic compounds such as pyridine, 2,2'-bipyridine (bipy), piperidine, and organo phosphines, arsines or stibinesO
The ruthenium catalyst is preferably utilized as homogeneous catalyst and therefore one criteria for the selection of the ruthenium compound in its solubility under the condition of reaction in the mixture of the nitrogen-containing organic compound, the hydroxyl-containing organic compound and the primary amino compound. The ruthenium compound is also selected with a view toward the catalytic activity o-f the compound. Thus the organo phosphines are useful ligands for incorporation into the ruthenium catalyst utilized in the process of the instant invention.

- lla - 275~8-lD
Suitable organophosphine include compounds represented by the following formula:
V (R3) (R4) P (Rs) wherein R3, R4 and Rs are radicals independently selected from the group consisting of hydrogen, hydrocarbyl, and substi-tuted deriva-tives of hydrocarbyl radicals, and wherein the substituted hydro-carbyl radicals may include heteroatoms selected from the group consisting of halogen, oxygen, sulfur, nitrogen and phosphorous atoms. Preferably the 3L~5~6~

above hydrocarbyl radicals will comprise from 1 to abou-t 20.carbon atoms, e.g. Erom about 1 to about 10 carbon atoms. Suitable radicals include methyl, ethyl, n-propyl, isopropyl, butyl, 2-chlorobutyl, n-propoxy, 2-nitro pentyl, phenyl, fluorophenyl, o,m, and p-methylphenyl, etc.
Examples of suitable organophosphines include triphenyl-phosphine, methyldiphenylphosphine, tris o-chlorophenylphosphine, -tri-n-propylphosphine, tris~p-methoxybenzylphosphine, etc.
Examples of halide-free ruthenium compounds which are suitable as catalysts include:
Ru3 (CO)12 H4Ru~(CO)12 Ruthenium acetylacetonate Ru3 (CO)g~p(pc6H5)3]3 In the invention oE the divisional application the catalyst comprises a bis-phosphino ruthenium compound, i.e. a compound having ruthenium coordinated with at least one bis-phosphino ligand. For the reasons given above the bis-phosphino ruthenium compound, utilized as the catalyst is also preferably free of halide.
The bis-phosphino ruthenium compound may also include the anions and/or the other ligands discussed above.
The bis phosphino ligand of the ruthenium catalyst may be represented by the general formula:

(R3) (R4) P-R6 ~ P (R3) (R~) wherein R3 and R~ are defined above and R6 is a divalent radical providing sufficient spacing to enable both phosphorous atoms to

5'~

~`
coordinate with a ruthenium atom~ Preferably, R5 comprises from 2 to 6 carbon atoms.
Examples of suitable bis-phosphine ligands include bis-(1,2-diphenylphosphino)benzene, bis(l,2-diphenylphosphino)ethane, bis(l,3-diphenylphosphino)propane, etc.
The bisphosphino ruthenium catalyst may be preformed or formed in-situ in the reaction solution by separately dissolving a bisphosphino-free ruthenium compound and a bisphosphine. Since the bisphosphino ruthenium compound is utilized in very low concentration, it is preferred tha-t the bisphosphino ruthenium compound is performed to ensure that the bisphosphino ligand will be coordinated with the ruthenium atom during the reaction.
No particular limitation is placed on the amount of pri-mary amine used. However, it is preferably used in an amount equal to from 0.1 to 100 moles per gm-atom of nitrogen in the nitrogen-containing organic compound.
The processes o~ the inventions of the parent and divis-ional applications may be carried out in the absence of solvent but the use of a solvent is not precluded. Suitable solvents include, for example, aromatic solvents such as benzene, toluene, xylene, etc.;
nitriles such as acetonitrile, benzonitrile, etc.; sulfones such as sulfolane, etc.; halogenated aliphatic hydrocarbons such as 1,1,2-trichloro-1,2,2,-trifluoroe-thane, etc.; halogenated aromatic hydro-carbons such as monochlorobenzene, dichlorobenzene, trichlorobenzene, etc.; ketones; esters; and other solvents such as tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, etc.
In carrying out the processes the hydroxyl-containing organic compound and carbon monoxide may be used in amounts equal 7 ~.
` -14- 27558-1 to at least 1 mole per gm-atom of nitrogen in the nitrogen~
containing compound. Preferably the hydroxyl-containing organic compound is used in excess and functions as a solvent as well as reactant.
The amount of the ruthenium compound used as the catalyst may vary widely according to the type thereo~ and other reaction conditions. However, on a weight basis, the amount of catalyst is generally in the range of from 1 X 10 5 to 1 part, and preferably from 1 X 10 4 to 5 X 10 1 parts per gram-atom of nitrogen in the starting nitrogen-containing organic compound when expressed in terms of its metallic component.
The reaction temperature is generally held in the range of 80 to 230 C., and preferably in the range of from 130 to 200C.
The reaction pressure, or the initial carbon monoxide pressure, is generally in the range of from 10 to 1,000 kg/cm G, and preferably from 30 to 500 kg/cm G..
The reaction time depends on the nature and amount of the nitrogen-containing organic compound used, the reaction temp-erature, the reaction pressure, the type and amount of catalystused, the type of reactor employed, and the like, but is generally in the range oE from 5 minutes to 6 hours. After completion of the reaction, the reaction mixture is cooled and the gas is dis-charged from the reac-tor. Then, the reaction mixture is subjected to any conventional procedure including fll-tration, distillation, or o-ther sui-table separation steps, whereby the resulting urethane is separated from any unreacted materials, any by-products, the solvent, the catalyst, and the like.

~2~6~)7 -14a- 27558~1 The urethanes prepared by the process of the invention have wide applications in the manuEacture of agricultural chemicals, isocyanates, and polyurethanes~
The invention of the parent and divisional applications are more fully illus-trated by the following examples~ However, they are not to be construed to limit the scope of the inventions~
In each of the following examples, the reaction was conducted in batch mode in a 300 ml stainless steel autoclave reactor equipped with a stirring mechanism which provides constant dispersion of the gas through the liquid solution. Heating of the reaction is provided by a jacket-type furnace controlled by a proportioning controller. The autoclaye is equipped with a high pressure sampling system Eor removal o~ small samples of the reaction solution during the reaction in order to monitor the reaction progress and determine reaction rates. Reaction samples were analyzed by gas chromatography~

C)7 - 15 - 27558-lD
EXA~PLE _ 75 ml of solution containing 6.16 g (0.050 mole) of nitrobenzene, 4.66 9 (0.050 mole) of aniline, and 2.68 g of t-butylbenzene (internal standard for gas chromatographic analyses) in methanol and 0.128 g Ru3(CO)12 (600 microgram-atoms of ruthenium) were placed in the reactor vessel. The gas volume in the vessel was replaced with carbon monoxide and then pressur-ized with carbon monoxide to 1000 psig at ambient temperature.
The reactor contents were -then heated to 160 C. The initial turnover frequency at this temperature was determined to be 0.36 mo'es nitrobenzene converted per gram-atom ruthenium per minute.
After 4.5 hours at 160 C., nitrobenzene conversion was complete and the solution contained 0.037 mole methyl-N-phenyl carbamate (74% selectivity based on nitrobenzene), 0.059 mole aniline (18%
selectivity based on nitrobenzene), and 0.003 mole total of formylidene aniline plus N-methyl aniline (6% selectivity).

The procedure is the same as for ~xample 1 with the exception that no aniline is introduced to the reaction.
Additional methanol was added so that the total initial solution volume is again 75 ml. The initial turnover frequency a-t 160 C.
is 0.10 moles ni-trobenzene converted per gram-atom ruthenium per minute. Complete nitrobenzene conversion requires 12 hours at 160 C. Selectivities based on nitrobenzene are ~4 percent to phenyl urethane (methyl-N-phenyl carbamate), 58 percent to aniline, and 11 percent total to formylidene aniline plus N-methyl ~5~ 7 - 16 - 27558-lD
aniline. The balance is converted to higher molecular weight products derived from aniline.
It is thus clear that the rate of conversion of nitrobenzene and the selectivity of the conversion of nitrobenzene to the corresponding urethane is increased by providiny the corresponding primary amine in the reaction solution.

For these examples, the procedure is the same as for Example 1 with the exception that various halide-free ruthenium compounds and various ruthenium catalyst loadings are used. The results obtained are given in table 1.

~' ~ U~
.
o o ~
4r~ ~r CO O (~ o .~ N
~ O
r-l ~ ~
Z

C~
~ oo ~0 ~
U~ O CO
'~ ~ O O O O O

H L~

~ _ .
C~ ~
~i r ~ I~
O
~1 L g o o ;~ ~ ~ ~D
o -1~
~) -_ ~ 8 ~-,~

~5~)7 - 18 - 27558-lD

The procedure is the same as for Example 1 with the exception that 0.24 g tris (acetylacetonate) ruthenium (600 ug-atoms ruthenium) is used as a catalyst precursor. After an initial induction period, the rate of nitrobenzene conversion reaches 0.47 moles nitrobenzene per g-atom ruthenium per minute.
After 6 hours at 160 C., nitrobenzene conversion is complete.
Selectivities based on nitrobenzene are 65 percen-t to phenylur-ethane, 26 percent to aniline, and 9 percent to formylidene anilineO l'his example demonstrates that ruthenium compounds, that do not contain carbon monoxide ligands, are useful as catalysts in the process of this invention' however, an induction period may be necessary to convert such ruthenium compounds -to the carbonyl.

The procedure is the same as for Example 1 with the exception that 0.13 g ruthenium trichloride (630 ug-atoms ruthenium) is introduced as catalys-t. After 5 hours at 160 C., nitrobenzene conversion is 7 percent with 100 percent selectivity to aniline. Complete nitrobenzene conversion requires 24 hours and gives 38 percent selectivity to phenyl urethane and 2L percent selectivity to aniline. I'he balance is converted to higher molecular weight materials.

The procedure is the same as for Example 1 with the exception that 0.154 g [Ru(CO)3C12]2 (600 ug-a-toms ruthenium) is ~7~7 - 18a - 27558-lD
introduced as catalyst. After 5 hours a-t 160 C., nitrobenzene conversion was 8 percent with 100 percent selectivity to aniline.

The procedure is the same as for Example 1 with the exception that both 0.128 9 Ru3(C0)12 and 0.126 9 RuC13 are introduced to the reaction. After 5 hours of reaction .~

-l9~ a~7 2755~

at 160 C., nitrobenzene conversion is 40 percent.
Selectivity to phenyl urethane is 47 percent. Selectivity to aniline is 53 percent. This example demonstrates that halide salts, even ruthenium halides, can adversely affect the conversion and selectivity of the otherwise effective catalyst of ~xample 1.
.

The procedure is the same as for Example 1 with the exception that both 0.043 g Ru3(CO)12 and 0.036 g PdC12 are introduced to the reaction. After 5 hours reaction at 160 C., nitrobenzene conversion is 10 percent. Selectivity to phenyl urethane is 5 percent. Selectivity to aniline is 95 percent~ This example demonstrates the difference between the prior art palladium catalyst and the catalysts used in the process of this invention. In particular, it would appear that the mode of action o~ the ruthenium catalysts described herein and the prior art palladium catalyst differ significantly in that the individual catalytic effectiveness of each is hindered by combinatlon with the other.

The procedure is the ame as for Example 1 with the exception that the initial carbon monoxide pressure at ambient temperature is 500 psig. Nitrobenzene conversion was complete after 6 hours at 160 C. and selectivity to phenyl urethane is 68 percent. This example demonstrates that a lower partial pressure of carbon monoxide may be used, with only a sli~ht decrease in rate o~ reaction and selectivity to urethane.

The procedure was the same as for ~xample 1 with the exception that 5.36g (0.050 mole) of p-toluidine was used instead of aniline. After 3 hours at 160 C, nitrobenzene conversion was complete and the solution ~57~07 - 20 - 27558-lD
contained 0.013 ~lole methyl-N-phenyl carbamate, 0.031 mole methyl-N-(tolyl) carbamate, 0.037 mole aniline and 0.019 mole p-toluidine. This example shows t'hat when the primary amine does not correspond to the nitro compound, mixtures o-f urethanes may be obtained.

The procedure is the same as for Example 1 with the exception that 6.86 g p-nitrotoluene and 5.36 g p-toluidine are used as the nitroaromatic and arylamine. Nitrotoluene conversion is 100 percent after 3 hours at 160 C. Selectivity to me-thyl N-p-tolylcarbamate is 88 percent. Selectivity to p-toluidine is 10 percent. This example demonstrates that certain primary amines are more efficient in increasing the rate of reaction than o-thers.
For example, substituents such as p-CH3, having a op of -0.17, or substituents having a more negative Hammet o value, increase the rate of corlversion of the nitroaromatic compound.

6.16g (0.050 mole) nitrobenzene and 10.6 g (0.050 mole) N,N'-diphenyl urea were reacted in methanol by the procedure given in Example 1. The catalyst was 0.126 g (200 micromoles) of [bis(1,2-diphenylphosphino)benzene] ru-thenium -tricarbonyl. As the reaction contents were heated to 160 C. most of the N,N'-diphenyl urea was converted to equal parts aniline and phenyl urethane. The rate of nitrobenzene conversion at 160 C. reached 0.86 moles nitrobenzene converted per mole rut'henium per minute. After 5 hours at 160 C. nitrobenzene conversion was 100 percent and the ~7~7 - 20a - 27558-lD
solu-tion contained 0.092 moles phenyl urethane and 0.048 moles aniline. This e~ample demonstrates that a urea, which decomposes to provide a primary amine, i.e. aniline, in-situ, also increases the rate of conversion of nitrobenzene, and the selectivity of the conversion of nitrobenzene to the urethane.

~5~37 12.3 g (0.100 molé nltrobenzene) in 75 ml of methanolic solution and 0.128 g Ru3(CO)12 (600 microgram-atoms ruthenium) were placed in the reactor vessel. The gas volume in the vessel was replaced with carbon monoxide and then pressurized at ambient temperature with 920 psig carbon monoxide and 80 psig hydrogen (approximately 0.05 mole hydrogen). The reactor contents were then heated to 160 C. Initially, aniline was produced îrom nitrobenzene in 100 percent selectivity. After approximately 0.030 moles aniline had been produced, phenyl urethane production also began. After a total of 7.5 hours at 160 C., nitrobenzene conversion was complete and the solution contained 0.060 moles aniline and 0.034 moles phenyl urethane. This example demonstrates that the primary amine may be provided by reduction of the nitrogen-containing oryanic compound, e.y. nitrobenzene, in-situ. Note that, once the added hydroyen is utilized to reduce the nitrobenzene to aniline, the selectivity of the conversion of the remaining nitrobenzene to the urethane is yreater than 50 percent.

E~A~IPLE 18 12.3 g (0.100 mole~ nitrobenzene and 0.90 g (0.050 mole) water in 75 ml methanolic solution and 0.128 g Ru3(CO)12 (600 microgram atoms ruthenium) were reacted under carbon monoxide as described in Example 1. When the reaction solution reached 160 C., 0.030 moles of aniline were present and phenyl ure-thane produc-tion began. After 6 hours at 160 C., nitrobenzene conversion was complete and the solution contained 0.061 moles aniline and 0.034 moles phenyl urethane. This example demonstra-tes that water can be utilized -to provide hydrogen to reduce the nitrogen-containing organic compound (nitrobenzene) to the primary amine (aniline), in-situ. Again, as in Example 1~, once substantially all of the hydrogen equivalents generated by the water-yas shift reaction are utilized to reduce ~L~57~ 7 nitrobenzene to aniline, the selectivity of -the conversion of the remaining nitrobenzene to the urethane is greater than 50 percent.

75 ml of solution containing 6.16 g (0.050 moles) of nitrobenzene, 4.66 g (0.050 moles) of aniline, and 2.68 g t-bu-tylbenzene (internal standard for gas chromatographic analysis) in methanol and 0.350 g of [bis(1,2-diphenylphosphino)ethane] ruthenium tricarbonyl (600 rnicrogramatoms of ruthenium) are placed in the reaction vessel. The gas volume in the vessel is replaced with carbon monoxide and then pressurized to 1000 psig at ambient temperature. The reactor contents are then heated to 160 C. The initial turnover frequency at this temperature is determined to be 0.85 moles nitrobenzene converted per g-atom ruthenium per minute. After 90 minutes at 160 C., nitrobenzene conversion is complete. Selectivity to methyl N-?henyl carbamate is 88 percent based on nitrobenzene converted.

In comparing this example to Example 1 it is diacovered that the use of a bisphosphino ruthenium compound as the catalyst for the conversion of the above-defined nitrogen-containing organic compound, e.g. nitrobenzene, to a urethane, in the presence of a hydroxyl-containing organic compound, e.g. methanol, and a primary amine, results in an increased rate of reaction and selectivity as compared -to a bis-phosphine-free ruthenium compound.

For -these examples, the procedure is -the same as for Example 19 with the excep-tions that various ruthenium compounds containing Group V ligands are used as catalyst precursors. The results are ~iven in Table 2.

- 23 - ~ 76~ 7 27558-lD

o v0 `9 o ~ ~ ~ d~ ~ ~ ~ ,~ ~ ~ o ~ ~ o o o o o o o o o o 0 ~ 9 .,, ,~
H
-'~ ~
.~
V I O O O O O O O O O O O
~ 0 ~ ~9 o 2 2 2 ~9 ,~ ~
.~ 0 _ V ,~

1-- N N r~ 0 -- O --` U
'S a ~
V ~ ~ C ~ ~0 ~ ~ ~ v ,~ ~ ~ v .~ S ~ S ~
s ~ c ~ ~ a) ~ 'C I ~ ~ 'C '~ ,c ~ a) ~ r-l a) `~ ~ ~ Q) u h (1) 1 ~ S ~ r-~ ~ S ~ ,C ~ ~ ~ ~ I C ~ ~ ~ h U U
~i 0 .LI 0 U 0 V 0 U 0 .IJ 0,~:; 0 JJ 0 0 _ .IJ 0 .,~ _ 0 Q h Q h Q h Q h Q h Q ~ Q h ~4 ~ 'Q h h U Q ~ O

9 t- co ~ o ~3 ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~1 24 ~.5~6~ 27558-1 The follo~ing conclusions are ob-tainea from the data summari7.ed in Table 2 and Example 19.
The ruthenium compounds having a, bis phosphino ligand, i.e. a bidentate phosphino ligand, provide increased reactivity as compared to ruthenium compounds having mono dentate phosphino ligands and tri dentate phosphino ligands. (For example, compare Example 19 with Examples 27, 28 and 29.) Aryl-substituted bi-dentate phosphino ligands provide more reactive ruthenium catalysts than their alkyl-substituted analogues. (Compare Example 22 with Examples 24 and 25.) The bi-dentate arsino ligands do not provide as active a ruthenium catalyst as the phosphino analogues. (Compare Example 24 with Example 26.) Halide-containing anions and Lewis acids r,educe the activity of the ruthenium catalysts utilized. (Compare Example 28 with Example 30.) Moreover aniline rather than urethane was the major product of Example 30.
A comparison of Example 28 and Example 22 demonstrates that two monodentate phosphino ligands do not provide as active a catalyst as a single bis-phosphine ligand.
In view of the above, it is clear that ruthenium com-pounds comprising bis-phosphino ligands, especially aryl-substituted phosphino ligands, are more reactive catalysts~

~XAMPL~ 31 The procedure is the same as for Example 20 with the exception that the reaction temperature is 169 C. This initial turnover fre~uency at this temperature is 1~9 moles nitrobenzene ~L~57~
-24a- 27558-1 converted per gram-atom ruthenium per minute. This example demonstrates that the reactivity of the catalyst utilized may be ~5~ 7 increased, without detrimental effect, by increasing the temperature o~ the reaction.

EXA~lPLE 32 The procedure is the same as for Example 19 with the exceptions ~hat 0.063 g (100 micromoles) [bis(1,2-disphenylphosphino)benzene]ruthenium tricarbonyl is used as catalyst and the reaction temperature is 177 C.
The initial turnover frequency at this temperature is 2.8 moles ni-trobenzene converted per gram-atom ruthenium per minute. This example also demonstrates that the reactivity of the ruthenium catalyst may be increased (significantly) by increasing the temperature of the reaction.

EXA~PLE 33 The procedure is the same as for Example 22 wi-th the exception that the initial carbon monoxide pressure at ambient temperature is 500 psig. The initial turnover frequency at 160~ C. is 1.1 moles nitrobenzene converted per gram-atom ruthenium per minute. At 100~ nitrobenzene conversion, selectivity to phenyl urethane is 85%. This example demonstrates that lower pressures of CO may be used successfully in the process of this invention.

6.16 g (0.050 mole) nitrobenzene and 10.6 g (0.050 mole) N,N'-diphenyl urea were reacted in methanol by the procedure given in Example 19. The catalyst was 0.126 g (200 micromoles) of [bis(1,2-diphenylphosphino)benzene]
ruthenium -tricarbonyl. As the reaction contents were heated to 160 C. most of the N,N'-diphenyl urea was converted to equal parts aniline and phenyl urethane. The rate of nitrobenzene conversion at 160C reached 0.86 moles nitrobenzene converted per mole ruthenium per minute. After 5 hours at 160 C, ni-trobenzene conversion was 100% and the solution contained 0.092 moles phenyl urethane and 0.048 moles aniline. This example demonstrates that bis-phosphine 5~

- 26 - 27558-lD
containing ruthenium catalysts give an increased rate of reaction when primary amine is formed in the reaction by in-situ decomposition of urea.

The procedure was the same as for Example 19 with the exception that 5.36 g (0.050 mole) p-toluidine was used instead of aniline. The initial turnover frequency at 160 C. was 1.0 moles nitrobenzene converted per g-atom ru-thenium per minute. After 70 minutes at 160 Cl nitrobenzene conversion was complete and the solution contained 0.014 mole methyl-N-phenyl carbamate, 0.028 mole methyl N-(p-tolyl) carbamate, 0.032 mole aniline, and 0.021 mole p-toluidine. This example shows that when a primary amine is supplied which does not correspond to the nitro compound, mixtures of urethanes may be obtained.

Claims (13)

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

1. A process for converting a nitrogen-containing organic compound, selected from the group consisting of nitro, nitroso, azo, and azoxy compounds, into the corresponding urethane, by reacting a solution containing said nitrogen-containing organic compound and a hydroxyl-containing organic compound with carbon monoxide, in the presence of a ruthenium catalyst compris-ing a bis-phosphine ligand, at conditions sufficient to convert said nitrogen-containing organic compound into the corresponding urethane.

2. The process of claim 1, wherein said nitrogen-containing organic compound is a nitro compound.

3. The process of claim 2, wherein said nitro compound is an aromatic nitro compound.

4. The process of claim 3, wherein said solution comprises a primary amine.

5. The process of claim 4, wherein said primary amine is an aromatic amine.

6. The process of claim 5, wherein said aromatic nitro compound is selected from the group consisting of nitrobenzene, nitroanisole, dinitrotoluene, nitromesitylene, bis (4-nitrophenyl) methane, nitro aminotoluene and nitro-carboalkoxyaminotoluene.

7. The process of claim 1, wherein said bis-phosphine ligand is selected from the group consisting of bis (1,2-diphenylphosphino) ethane, bis (1,3-diphenylphosphino) propane and bis (1,2-diphenylphosphino) benzene.

8. The process of claim 4, wherein said primary amine is provided by reduction of said nitrogen-containing compound with hydrogen in said solution.

9. The process of claim 4, wherein said primary amine is provided by reduction of said nitrogen-containing compound with hydrogen equivalents derived from the ruthenium-catalyzed water-gas shift reaction.

10. The process of claim 4, wherein said amine is select-ed from the group consisting of p-toluidine, aniline, diamino-toluene, bis- (4-aminophenyl) methane, aminonitrotoluene, and aminomethylcarboalkoxybenzene.

11. The process of claim 4, wherein said amine is provid-ed by decomposing a urea or biuret in-situ.

12. The process of claim 1, wherein said nitro-containing organic compound is converted into the corresponding urethane, by reacting said solution with carbon monoxide at a temperature of at least about 130°C and a carbon monoxide pressure of at least about 200 psig.

13. The process of claim 1, wherein said bis-phosphine ligand is a bis (diarylphosphine) chelate ligand.