3,381,023 United States Patent Office Patented Apr. 30, 1968 1. 2 Furthermore, the isolation procedures for separating the 3,381,023 resulting compounds are simplified by the process of this PREPARATION OF AROMATIC GROUP VI-B METAL TRICARBONYS invention, as a minimum of unreacted starting materials Mark Crosby Whiting, Oxford, England, assignor to and side products are present in the final composition. In Ethyl Corporation, New York, N.Y., a corpora addition, Superior yields are obtained. For example, tion of Virginia O-cresyl methylether chromium tricarbonyl was prepared No Drawing. Filed Mar. 10, 1958, Ser. No. 720,083 in 99 percent yield by the process of this invention. Yields 31 Claims. (Ci. 260-429) of this order of magnitude have not heretofore been pos sible. This invention relates to a process for the preparation The temperatures employed in the process of this inven of organometallic compounds and more particularly the O tion may vary over a wide range. In general, tempera preparation of aromatic Group VI-B transition metal tures of from about 100° C. to 300° C. are employed. carbonyl compounds. However, a preferred range of temperature is from Recently a method for the preparation of aromatic 150 C. to 225 C. as the reaction in this temperature chromium tricarbonyl compounds has been proposed, 5 range leads to a high yield of products with a minimum which method comprises the equilibration, in an aromatic of undesirable side reactions. Solvent of a di-aromatic chromium compound with chro The aromatic compound which is a reactant in the mium hexacarbonyl and which employs a reaction time process of this invention can be selected from a wide of 12 hours under pressure at temperature in excess of range of aromatic organic compounds including mono 200 C. In order to accomplish this preparation, it is 20 nuclear hydrocarbons, poly-nuclear hydrocarbons, mono first necessary to prepare di-benzene chromium itself, and poly-nuclear aromatic amines, aromatic esters, aro which is a complex and inefficient process. matic ethers and phenolic compounds. The applicable aro It is, therefore, an object of this invention to provide matic compounds should be free of oxidizing substituents a novel method for the preparation of aromatic Group and be less acidic than benzoic acid. Examples, therefore, VI-B transition metal carbonyl compounds. A further 25 of the applicable aromatic compounds include phenol, object is the preparation of aromatic chromium tricar amylbenzoate, propylbenzoate, butylphenyl ether, para bonyi compounds which does not first require the prepara methyl anisole, n-hexylaniline, 2-amino-4-isopropylnaph tion of a di-aromatic chromium compound. Other objects thalene, N,N-di-methyl-o-methylaniline, 1 - methyl - bi will be apparent from the following description. phenyl, tetrahydronaphthalene, 6-methylnaphthalene, an The above and other objects are accomplished by a 30 thracene, phenanthracene, mesitylene, meta-di-methylben process for preparing an aromatic Group VI-B transi Zene, m, m'-di-tert-butyl-diphenyl and the like. Those aro tion metal carbonyl coordination complex which com matic compounds having up to about 20 carbon atoms are prises reacting a Group VI-B transition metal carbonyl preferred since they lead to more easily recoverable with an aromatic compound. It has now been found that products and are, of course, the principal available aro this preparation may be accomplished in a system where matic compounds. A preferred embodiment of this inven the only reactants are the Group VI-B transition metal tion employs an aromatic compound in which the sub carbonyl and the aromatic compound. When desired, the stituents on the benzene nucleus, if any, are not para reaction can be conducted in a high-boiling solvent. oriented. Thus preferred aromatic compounds employed The process of this invention can be summarized by the have substituents in the meta or ortho relationship, as it following chemical equation in which Ar represents an 40 has been found that higher yields of aromatic Group aromatic compound and M represents a Group VI-B VI-B transition metal carbonyl compounds can be pre transition metal: pared from these reactants. Whereas the process of the present invention can be Ar--M(CO)6) ArM(CO)3--3CO conducted at atmospheric pressure at the reflux tempera Thus, carbon monoxide is given off as a product of the 45 ture of the system, higher or lower temperatures and reaction. higher pressures may also be conveniently employed. Thus The Group VI-B transition metal carbonyl compounds benzene chromium tricarbonyl has been prepared by reac which are reactants in the process of this invention in tion of benzene with chromium hexacarbony in a sealed clude chromium hexacarbonyl, molybdenum hexacar vessel at 225 C. at the prevailing pressure. In this em bonyl and tungsten hexacarbonyi. A preferred embodi 50 bodiment of the invention, temperatures of from 150 C. ment of this invention comprises the reaction of chro to 250 C. are preferred although temperatures outside mium hexacarbonyl with an aromatic compound to pro this range may also be employed. Since carbon monoxide duce an aromatic chromium tricarbonyl. This embodi is given off as a product of this reaction, and an excess of ment is preferred as the compounds prepared are highly carbon monoxide pressure may inhibit further formation useful chemical entities. of the desired aromatic Group VI-B transition metal tri As an example of the preferred embodiment of the carbonyl compound, it is advantageous to vent excess car process of this invention, a suspension of chromium hexa bon monoxide through a condenser when the process of carbonyl in an excess of anisole was heated under reflux this invention is conducted at elevated pressures. in a nitrogen atmosphere until sublimation of the chro A particularly preferred embodiment of this invention mium hexacarbonyl had ceased, resulting in a deep yel 80 comprises reacting under reflux conditions at atmospheric low-colored solution. This solution was evaporated to pressure, an aromatic organic compound, as defined dryness under reduced pressure leaving a yellow crystal above, which contains at least seven carbon atoms with a line residue which comprised a 94 percent yield of anisole Group VI-B transition metal carbonyl. It has been found chromium tricarbonyl. This compound has a melting point that when the aromatic compound employed has a mo of 86-87 C. lecular weight of above 90 it is unnecessary to employ The process of this invention has numerous advantages. elevated pressures to obtain an excellent yield of an aro It is a simple and straight forward reaction to obtain the matic Group VI-B transition metal tricarbonyl com desired products. In distinction to previously known meth pound. When the aromatic compound employed has a mo ods for making the compounds, it is conducted in a single lecular weight of below about 90, it is preferred to con step beginning with the metal carbonyl. As pointed out 70 duct the process at slightly elevated pressures as described above, the previous method involved the initial prepara above, as it has been found that superior yields of the tion of a di-aromatic metal compound as an intermediate. lower molecular weight aromatic Group VI-B transition 3,381,023 3 4. metal tricarbonyl compounds are formed in this manner. for six hours while the reactants were protected by a No solvent is required in conducting the process of stream of nitrogen. The reaction was conducted in a glass this invention, the aromatic compound being employed in reaction vessel fitted with a reflux condenser and heating excess to serve as a carrier for the Group VI-B transition means. The resulting deep yellow solution was cooled and metal carbonyl. However, it is often convenient to em diluted with 713 parts of ethylether and then filtered. The ploy an inert diluent in the process. High-boiling satu resulting solution was evaporated to dryness under re rated hydrocarbons are the preferred solvents. Other sol duced pressure. One hundred thirty-five parts of yellow vents which can be employed include higher boiling crystalline solid were obtained which had a melting point ethers, high-boiling aliphatic esters, silicone oils, aliphatic of 86-87 C. after recrystallization from isopropylether. polyesters, and other liquids inert to the primary re This represents a 94 percent yield of anisole chromium actants. Examples of the compounds useable as solvents 0 tricarbonyl. Elemental analysis of the compound showed in the process of this invention include n-octane, n-no it to contain 49.5 percent carbon and 3.5 percent hydro nane, n-decane and the various iso-decanes and other gen as compared to a calculated content of 49.2 percent parafinic hydrocarbons having up to about 20 carbon carbon and 3.3 percent hydrogen. atoms such as eicosane, octadecane, pentadecane and the 5 Examples II-VIII like. Ether solvents which may be employed include ethyl octylether, amyl ethyl ether, ethyl heptylether, and ethyl Following the basic procedure outlined in Example I hexylether. Ester solvents which may be employed in above, aromatic chromium tricarbonyl compounds of clude pentyl 2-methylpropanoate, pentyl butanoate, butyl mesitylene, o-xylene, m-xylene, para-xylene, tetralin, o butanoate, y-methylbutyl butanoate, ethyl decanoate, cresyl methylether, and para-cresyl methylether were ob methyl decanoate, pentylhexanoate, ethylhexanoate, and 20 tained. The details of these preparations are given in the like. Applicable silicone oils include copolymers and Table I. The reactions were all conducted at the reflux homopolymers of the various organosiloxanes and or temperature of the system. In each instance where the ganosilanes having the appropriate boiling range. Exam product was analyzed for its elemental constituents, re ples of these are the dimethyl polysiloxanes, methylphen 25 sults exceptionally close to the theoretical content were yl polysiloxanes, diphenyl polysiloxanes, di(chlorophen obtained. TABLE I Reaction Melting Yield Example Aromatic Reactant ine Product Point (C.) (Percent) (Hours) II------Mesitylene.------4. Mesitylene chromiurn tricarbonyl------177-78 86 III------0-Xy 6 o-Xylene chromium tricarbonyl------90-95 8. V- 6 In-Xylene chronium tricarbony------07-08, 5 27 V---- 6 p-Xylene chromium tricarbonyl------98–99 2 WI 3. Tetralin chromium tricarbonyl------116-117.5 84 VII------o-Cresyl methylether------, 3 Ogi; methylether chromium tricar- 75-77 99 Onyl. VIII------p-Cresyl methylether------4.5 p-Cresylcarbonyl. methylether chromium tri- 47-48.5 70 yl)polysiloxanes, hexaethyldisiloxane, hexapropyl di- Example IX silane, diethyldipropyldiphenyldisilane and the like. The The procedure of Example I was followed employing polyesters applicable as solvents in the process of this 40 methyl benzoate and chromium hexacarbonyl. Methyl invention are completely esterified dicarboxylic acids. benzoate chromium tricarbonyl was produced by this Esters may be employed derived from succinic, maleic, reaction. pyrotartaric, glutaric, adipic, pimelic, suberic, azelaic, Example X sebacic and pinic acids, specific esters being di(1-methyl 4-ethyloctyl)glutarate, di(2 - ethylhexyl)adipate, di(3- 45 A mixture of 21 parts of chromium hexacarbonyl and methylbutyl)azelate, di(2-ethylhexyl)azelate, di(2-ethyl 38 parts of N,N-dimethylaniline was heated to reflux in hexyl)sebacate, di(3,5,5-trimethylhexyl)sebacate, di(2- 179 parts of decalin (decahydronaphthalene) for 3 hours. ethylhexyl)maleate, di(methylcyclohexyl)adipate, 2 The solution was then cooled and made homogeneous ethylhexyl-1-methylheptyl sebacate, and the like. with ether, filtered and concentrated to a small volume. The aromatic Group VI-B transition metal carbonyl 50 A yellow solid precipitated from the solution and was re compounds prepared by the process of this invention can moved by filtration. This solid was N,N-dimethylaniline be recovered by evaporation of the excess aromatic re chromium tricarbonyl which had a melting point of 145.8- actant and/or solvent when the product is soluble in the 146.5 C. after recrystallization from isopropyl ether. system. In certain cases, the product aromatic metal car Twenty-two and six tenths parts of the compound were bonyl compound is insoluble in the solvent employed, and 55 recovered representing a 90 percent yield. Analysis showed the compound may be recovered by filtration. The com the compound to contain 51.3 percent carbon and 4.35 pounds may be purified by recrystallization from hydro percent hydrogen. The calculated content for N,N-di carbons or lower aliphatic ethers. methylaniline chromium tricarbonyl is 51.35 percent car The following examples, in which all parts and pre bon and 4.3 percent hydrogen. centages are by weight, are illustrative of the compounds 60 Examples XI-XVII of this invention and their preparation. The procedure of Example X was applied to other aro Example I matic reactants with similar results. The details of these A suspension of 138 parts of chromium hexacarbonyl reactions and the products obtained are shown in Table in 200 parts of anisole was heated under reflux (155° C.) 65 II. TABLE H" - lu Example Aromatic Reactant Reaction Product Melting Yield Time (hours) Point (C.) (percent)

H------Tetrain chromium tricarbonyl 1 66 Aniline chromium tricarbonyl. 73-175 9. O-Toluidine chromium tricarbonyl 30-32 98 XIV------m-Toluidine------n-Toluidine chromium tricarbonyi- 37-38.5 99 XV------N-methylaniline------N-methylaniline chromium tricarbonyl 122.5-124 89 XVI------N,N-dimethylaniline.------N,NinethylanilineOnyl. chromium tricar- 146-146.5 9. XVII.------N,N-dimethyl-o-toluidine------N,N-dimethyl-o-toluidine chromium tri- 76.5-78 97 carbonyi. Product is essentially the tetralin complex which results from hydrogen transfer from the solvent. 3,381,023 5 Example XVIII evidence of typical absorption bands for a metallo car Following the procedure outlined in Example X, 236 bonyl. parts of chromium hexacarbonyi and 144 parts of di Example XXVIII phenyl were reacted in 225 parts of decalin and the result Following the procedure of Example XXVII, tungsten ing mixture was subsequently diluted with 800 parts of carbonyl is reacted with excess toluene to give a good yield ethyl ether. The solution was concentrated to yield a red of toluene tungsten tricarbonyl. Excellent results are also oil which was triturated with an equal volume mixture obtained when m-Xylene is reacted at atmospheric pres of ether and pentane. The resulting orange powder had Sure with tungsten carbonyl in ethylhexylether as a sol a melting point of 171-172 C. Concentration of the re went at the reflux temperature of the system. maining filtrate to dryness produced another orange solid O The compounds of the present invention vary insofar having a melting point of 57–63 C. in 87 percent yield. as their thermal stability is concerned, but all of them can One of the products of this reaction is biphenyl chromi be decomposed at a temperature above 400° C. The ther um tricarbonyl and the other is cyclohexyphenyl chromi Imal decomposition of the compound results in the forma um tricarbonyl which results from hydrogen transfer from tion of metallic mirrors comprising a layer or coating of the decalin solvent to the biphenyl reactant. a particular Group VI-B transition metal. These metallic layers and coatings have useful and desirable properties Example XIX of electrical conductance, furnish protection against cor Molybdenum carbonyl was reacted in an excess of me rosion when they are applied to base materials susceptible sitylene at reflux to give 70 percent yield of mesitylene to corrosion and likewise have a decorative effect. The molybendum tricarbonyl. 20 compgunds of the present invention can also be deposited Examples XX-XXIV On giaSS, glass cloth, resins and other insulating supports, and the resultant metal-coated material can be used as Following the procedure outlined in Example XVIII, conductors and insulating tapes for electrical applica B-methylnaphthalene, cy-naphthylamine, 3-naphthylamine, tions. The metals can be deposited on the support in the phenanthrene, and anthracene were reacted with chromi desired proportions by thermal decomposition using clas um hexacarbonyl to give substantial yields of the corre sical processes in order to obtain the so-called “printed sponding aromatic chromium tricarbonyl complex. In all electrical circuits. Similarly the metals can be applied to these instances, the resulting product was a mixture of metallic Supports to increase the corrosion resistance and isomeric products which result from the fact that the aro on glass or asbestos cloth to obtain decorative metallic sur matic compound employed is poly-nuclear. 30 faces and designs. In order to effect the deposition of the Example XXV metals by thermal decomposition of the compounds of the present invention, it is preferred to use inert gasses, Following the procedure outlined in Example X, pheno! e.g., argon, as protecting or covering gas in order to re was reacted with chromium hexacarbonyl to give an excel duce to a minimum oxidation by air or oxygen. ent yield of hydroxybenzene chromium tricarbonyl. Deposition on glass cloth illustrates the applied proc Example XXVI esses. A glass cloth band weighing 1 gram is dried for one hour in an oven at 150° C. Then together with 0.5 gram Molybdenum hexacarbonyl (500 parts) was heated at of anisole chromium tricarbonyl it is enclosed in a glass Teflux in a mixture of about 3115 parts of Inesitylene and tube devoid of air and heated at 400° C. for one hour, 6600 parts of decalin under a nitrogen atmosphere. Re 40 after which time the tube is cooled and opened. The cloth fluxing was continued until all gas evolution had ceased. has a uniform metallic gray appearance and exhibits a The resultant green solution was cooled and a yellow gain in weight of about 0.02 gram. The cloth has a greatly crystalline solid precipitated. This was filtered and recrys decreased resistivity. Each individual fibre proves to be tallized from benzene to yield 280 parts of mesitylene a conductor. As would be expected, the application of molybdenum tricarbonyl. Analysis of the compound a current to the cloth causes an increase in temperature. showed it to contain 48.2 percent carbon, 4.00 percent hy Thus, a conducting cloth has been prepared. This cloth drogen and 32.0 percent molybdenum. The calculated can be used to reduce static electricity, for decoration, composition of nesitylene molybdenum tricarbonyl is for thermal insulation by reflection, as protection and as 48.0 percent carbon, 4.0 percent hydrogen and 32.0 per a heating element. cent molybdenum. The compound was submitted for in 50 The chemical entities of the present invention can be frared analysis and showed typical absorption bands for used to deposit the respective Group VI-B transition ele a metallo carbonyi. ments in the catalytic form on suitable supports. Thus, Example XXVII the compounds of the present invention can be thermally decomposed using elevated temperatures of 250 400° C. In a pressure resistant vessel equipped with heating 55 or above, preferably in an atmosphere of argon or other means, temperature measuring device and means for inert gas, e.g., krypton, in order to obtain supported Group charging and discharging gaseous, liquid and solid re VI-B transition elements in the catalytically active form. actants was placed 110 parts of chromium hexacarbonyl Other classical processes can be used to deposit the metal and 870 parts of benzene. The vessel was then sealed and lic catalysts, using the chemical entities according to the the temperature raised to 250 C. This temperature was 60 present invention. For example, a solution of mesitylene maintained for six hours with the charge under 100 p.s.i. molybdenum tricarbonyl is mixed with infusorial earth, of nitrogen pressure. The vessel was then cooled, vented the compound being adsorbed on the infusorial earth. The and discharged. Unreacted chromium carbonyl was fil adsorption product is separated by filtration and heated tered from the resulting benzene solution and the benzene in air to decomposition temperature of the mesitylene was removed by evaporation at reduced pressure. Follow 65 ing this the residue was sublimed at two millimeters of molybdenum tricarbonyl, yielding a catalytically active mercury pressure and 130° C. The first product to sublime Surface of molybdenum oxide. The catalyst is useful in the was a small amount of chromium hexacarbonyl following refining of petroleum fractions. The catalyst can also be which 16 parts of yellow crystalline benzene chromium deposited on alumina. tricarbonyl sublimed from the residue. The compound claim: has a melting point of 163-165 C. Analysis showed the 1. A process for preparing a carbocyclic aromatic compound to contain 24.4 percent chromium. The cal Group VI-B transition metal tricarbonyl compound culated chromium content for benzene chromium tricar which comprises reacting a Group Vi-B transition metal bonyl is 24.3 percent. An infrared spectra indicated that heXacarbonyl compound with a carbocyclic aromatic com the compound has the assigned structure and showed the 75 pound which is free of oxidizing Substituents and is less 3,381,023 7 8 acidic than benzoic acid in a system where the only re 22. The process of claim 2 wherein said carbocyclic actants are the said Group VI-B transition metal carbonyl aromatic compound is aniline. and the said aromatic compound. 23. The process of claim 2 wherein said carbocyclic 2. Process of claim where the Group VI-B transition aromatic compound is o-toluidine. metal carbonyl is chromium hexacarbonyl. 24. The process of claim 2 wherein said carbocyclic 3. Process of claim 1 wherein the reaction is conducted aromatic compound is m-toluidine. at the refluxtemperature of the system. 25. The process of claim 2 wherein said carbocyclic 4. Process of claim wherein the reaction is conducted aromatic compound is N-methylaniline. under pressure at above the reflux temperature of the 26. The process of claim 2 wherein said carbocyclic System. O aromatic compound is N,N-dimethyl-o-toluidine. 5. The process for the preparation of benzene chro 27. The process of claim 2 wherein said carbocyclic mium tricarbonyl which comprises reacting benzene with aromatic compound is diphenyl. chromium hexacarbonyl at 250° C. 28. The process of claim 2 wherein said carbocyclic 6. A process for preparing a carbocyclic aromatic aromatic compound is mesitylene. Group VI-B transition metal tricarbonyl compound which 5 29. Process for the preparation of mesitylene molyb comprises reacting a Group VI-B transition metal hexa denum tricarbonyl, said process comprising reacting carbonyl with a carbocyclic aromatic compound which is molybdenum hexacarbonyl with mesitylene. free of oxidizing substituents and is less acidic than ben 30. A process comprising reacting a carbocyclic aro zoic acid at a temperature ranging from 150 to 225 C. matic compound with chromium hexacarbonyl in accord in a system where the only reactants are said Group VI-B 20 ance with the equation transition metal hexacarbonyl and said carbocyclic aro matic compound. Ar--Cr(CO)6--> ArCr(CO)--3CO 7. The process of claim 6 wherein said carbocyclic aro wherein Ar represents said carbocyclic aromatic com matic compound contains up to about 20 carbon atoms. pound. 8. Process of claim 7 wherein said carbocyclic aro 25 31. A process comprising reacting a carbocyclic aro matic compound contains at least 7 carbon atoms and matic compound, with a Group VI-B metal hexacarbonyl has a molecular weight in excess of 90. in accordance with the equation 9. The process of claim 6 wherein the reaction is car ried out in the presence of a neutral solvent. Ar--M(CO)--> ArM(CO)3--CO 10. The process of claim 6 in which the carbocyclic 30 wherein Ar represents said carbocyclic aromatic com aromatic compound is selected from the group consisting pound and M represents said Group VI-B metal. of carbocyclic aromatic compounds in which the sub stituent groups are ortho oriented and carbocyclic aromatic References Cited compounds in which the substituent groups are meta UNITED STATES PATENTS oriented. 35 11. The process of claim 6 in which said Group VI-B 2,409,167 10/1946 Veltman ------260-429 X transition metal hexacarbonyl is chromium hexacarbonyl. 2,818,417 12/1957 Brown et al. ------260-429 12. The process of claim 2 wherein said carbocyclic aromatic compound is anisole. OTHER REFERENCES 13. The process of claim 2 wherein said carbocyclic 40 aromatic compound is o-xylene. Z. Anorg. Chem., 221, pp. 337 to 348 (1935). 14. The process of claim 2 wherein said carbocyclic JACS, vol. 76, Jan. 5, 1954, p. 209. aromatic compound is m-xylene. J. Chem. Soc. (London), February 1958, pp. 642, 643. 15. The process of claim 2 wherein said carbocyclic Fischer et al.: “Chem. Berichte,” it 12 (1958), pp. aromatic compound is p-xylene. 2763 to 2772. 16. The process of claim 2 wherein said carbocyclic Fischer et al.: “Chem. Berichte," ii.11, (1958), pp. aromatic compound is tetralin. 2395 to 2399. 7. The process of claim 2 wherein said carbocyclic Hallam et al.: “J. Inorganic and Nuclear Chemistry,' aromatic compound is o-cresyl methylether. 1955, vol. 1, p. 313. 18. The process of claim 2 wherein said carbocyclic 50 Piper et al.: "J. Inorganic and Nuclear Chemistry,' aromatic compound is p-cresyl methylether. 1956, vol. 3, p. 104 and vol. 1, 1955, p. 165. "Quarterly 19. The process of claim 2 wherein said carbocyclic Rev., vol. IX, No. 4, 1955, p. 408. aromatic compound is methyl benzoate. 20. The process of claim 2 wherein said carbocyclic TOBIAS E. LEVOW, Primary Examiner. aromatic compound is N,N-dimethylaniline. 55 ABRAHAM H. WINKELSTEIN, Examiner. 21. The process of claim 2 wherein said carbocyclic aromatic compound is naphthalene. R. S. AULL, H. M. S. SNEED, Assistant Examiners.