2,859,228 United States Patent Office Patented Nov. 4, 1958 2 plished by reacting a lead halide wherein the halide has an atomic weight greater than 35, that is the chlorides, 2,859,228 bromides, and iodides of lead, and mixed lead halides, with an organo metallic compound of group III A of the MANUEFACTURE OF ORGANOLEAD COMPOUNDS 5 periodic table, that is boron, aluminum gallium, and in Sidney M. Blitzer and Tillmon H. Pearson, Baton Rouge, dium, wherein the group II. A metal is the sole metal La., assignors to Ethyl Corporation, New York, N.Y., in the metallo organic compound. a corporation of Delaware In accordance with this invention, it has been dis covered that to produce organolead compounds it is un No Drawing. Application March 28, 1955 O necessary, to start with a lead alloy, or in fact to em. Seria No. 497,378 ploy metallic lead at all. Among the lead halides that 7 Claims. C.260-437) can be employed in the process of this invention are lead chloride, lead bromide, leadiodide, lead bromoiodide, lead chloroiodide, and lead chlorobromide. This invention relates to a process for the manufacture 5 The process of the present invention can best be under of organolead compounds. In particular, this invention stood by considering the: chemical equation involved. In is directed to an improved process for the manufacture general, the process proceeds according to the equation of tetraethyllead. The process employed in present commercial practice for the manufacture of tetraethylead has been in use for where R is an organic radical and X is halogen having a number of years and, in general, is satisfactory. How atomic weight greater than 35, and M represents a metal ever, it has certain disadvantages, which are overcome by of group III A of the periodic table, namely boron, practicing our invention. It proceeds by reacting a so aluminum, gallium, or indium. In the preferred embodi dium-lead alloy, of composition controlled to correspond ment of this process the organic radicals are hydrocarbons substantially to NaPb, with ethyl chloride according to 25 and particularly are non-aromatic or aromatic. Among the following equation: the non-aromatic.radicals we can employ alkyl or hydro carbon substituted alkyl radicals. In general, we prefer the lower alkyl radicals having up to about eight carbon With the highest yields obtained thereby, only about atoms. Among the aromatic radicals which can be em 22 percent of the lead present in the NaPb. alloy is con 30 ployed in the above reaction are included phenyl and hy verted to tetraethylead. Under conditions of best opera drocarbon substituted phenyl radicals such as the alkaryl tion of this process, no one heretofore, as far as we are radicals. In general, aromatic radicals having up to ten aware, has been able to increase this yield of tetraethyl carbon atoms are satisfactory. Thus, the compounds MR lead by even a few percent, due to the inherent limitation may be considered alkylating or arylating agents with re in yield as is apparent from the consideration of the 35 spect to the lead in the inorganic lead compound. above equation. It should be noted that in this reaction Of greatest current importance from a commercial at least 75 percent of the lead originally employed is not standpoint is the manufacture of tetraethylead by the proc alkylated. Thus, in this reaction, large quantities of lead ess of this invention. This embodiment can be illustrated must be recovered and reprocessed to NaPb alloy in or by reference to the following equation representing the der to make it economical. A further disadvantage of 40 preferred embodiment. such a large quantity of unreacted lead is that valuable reaction space in the reaction vessel is occupied by ma terials which are essentially inert for the manufacture of Illustrative of the alkylating or arylating agents which tetraethyllead under present conditions and mode of opera we can employ are trimethyl aluminum, trimethyl gal tion. 45 lium, trimethyl boron, trimethyl indium, triethyl alumi Other processes for the production of organolead com num, triethyl gallium, triethyl boron, triethyl indium, tri pounds, and in particular tetraethylead, have been de propyl aluminum, tripropyl gallium, tripropyl boron, tri vised to consume the lead produced in the above equa propyl indium, tributyl aluminum, tributyl gallium, tri tion. While such processes are satisfactory from the butyl boron, tributyl indium, triamy aluminum, triamyl. standpoint of lead consumption, they suffer an additional 50 gallium, triamyl boron, triamyl indium, and the like up to drawback in common with the present commercial proc about trioctyl aluminum, trioctyl gallium, trioctyl boron, ess in that they require organohalide as the ethylating trioctyl indium, triphenyl aluminum, triphenyl gallium, agent. One such process is that described in tJ. S. Patent triphenyl boron, triphenyl indium, tribenzyl aluminum, 2,535,190 wherein lead as, for example, that produced in tribenzyl gallium, tribenzyl boron, tribenzyl indium, tri-. the commercial process, is treated with metallic mag 55 tolyl aluminum, tritolyl gallium, tritolyl boron, tritolyl nesium and ethyl chloride in the presence of a catalyst indium, triphenethyl aluminum, triphenethyl gallium, tri preferably an alkyl ether. Thus, in this process as well phenethyl boron, triphenethyl indium, tributylphenyl alu as the present commercial process, the tetraethylead man minum, tributylphenyl gallium, tributylphenyl boron, tri ufacturing operation is restricted by the necessary balance butylphenyl indium, tri(diethylphenyl) aluminum, tri(di between the metallic sodium required and the organic 60 ethylphenyl) gallium, tri(diethylphenyl) boron, tri(die chlorine in the ethyl chloride. ethylphenyl) indium and the like. In addition to the nor It is therefore an object of this invention to provide a mal alkyl aluminum, boron, gallium and indium com process for the manufacture of organolead., compounds pounds indicated heretofore, the branched chain isomers which overcomes the above objections to the present com can be employed. Furthermore, mixed organo aluminum mercial process and those processes which have been pro 65 compounds can be employed to produce mixed organo posed more recently as an improvement thereover. Par lead-compounds. Such raw materials include, for ex ticularly, it is an object of the invention to increase the ample, dimethyl ethyl aluminum, dimethyl phenyl alumi conversion of lead to tetraethyllead above that obtained num, dibutyl phenyl gallium, diphenyl methylboron, and in present commercial practice without requiring the use the like. of metallic sodium, metallic lead, or alkyl halogen com 70 By the process of this invention, as much as 50 percent pounds. of the lead in the foregoing lead salts is directly converted These and other objects of this invention are accorn to organolead, or in particular, in a commercial embodi

m 3 - - - 4 ment, to tetraethyllead. The remaining portion of the of the product suitable for other applications or so that lead is in a highly active form as lead metal and is ideally they can be readily removed by distillation at a tempera suited for employment in the commercial process em ture at which the organolead compound will not decom ploying sodium-lead alloy or in that which proposes the pose. Other inert carrier liquids are satisfactory and reaction of metallic lead with an alkylating agent in the where the product is a liquid such as, for example, in presence of magnesium and a catalyst. Conversely, the the manufacture of tetraethyllead, the organolead com lead so produced by this invention can be recycled eco pound itself can be employed as a carrier liquid. In such nomically to the present process by conversion to the an operation, economies are effected by obviating the ne appropriate lead salt. W cessity of recovery by other means than merely filtration . Our invention is adaptable to the production of organo 0 of the co-produced solids. Another class of carrier liq lead compounds generally, such as tetraethyllead, tetra uids comprises the liquid amines, liquid ammonia, and methyllead, dimethyldiethyllead, tetraphenylead, triethyl ethers. The principal criterion of choice, therefore, of a phenylead and tetrapropyllead. Nevertheless, for con carrier is the physical characteristic of the organolead venience in describing our invention hereafter, specific compound produced, and the inertness of the liquid to reference will be made to tetraethylead, the most widely 5 the organo aluminum reactant. Certain of the afore known because of its use as an anti-knock agent. When in entioned reactant carriers, while inert to the reactants, ever, in the following description, this material is referred exhibit a beneficial effect on the reaction which may be. to, it is to be understood that other organolead com considered catalytic in nature and contribute to the ease pounds or mixtures can be made by our process. of reaction and rapidity of arriving at completion of the Likewise, aluminum triethyl is the preferred organic 20 reaction at relatively lower temperatures and pressures. . . reactant in the process of this invention and for conven In general, when conducting this process in the pres ience, sometimes hereinafter the invention will be de ence of a liquid carrier as above, the amount of carrier scribed with reference to the employment of aluminum should be proportioned so as to provide adequate heatre triethyl. However, when this material is referred to, it moval facilities. In general, the load on the heat trans is to be understood that the other group III A metals can fer medium is proportional to the concentration or rela be employed as the metallic organic reactant of this tive proportion of the reactants and carrier. In a batch process. operation, it is preferred to employ the liquid diluent in Generally, the process of this invention is conducted as the proportion of as much as 1,000 parts per part of follows. Into a reaction vessel, preferably a stirred auto organo metallic reactant. In a continuous operation or clave, is placed the desired quantities of organo metallic in an operation provided the maximum heat transfer compound, for example, an organo aluminum compound, medium, a more concentrated reaction mixture can be suspended or dissolved in an inert liquid carrier such as, employed wherein as little as equal parts by weight of for example, a hydrocarbon of medium boiling range. ... carrier and organo metallic reactant are employed. In The appropriate lead salt, for example lead chloride in general, it has been found that a more concentrated re finely divided solid form is introduced through a hopper 3 5 action mixture provides a rapid reaction and, provided containing a plugcock into the autoclave while agitating adequate heat removal means are provided, this is an ad to create a suspension of the lead compound in the inert vantage as the organolead product is subjected to the liquid carrier. The connection to the hopper is thereupon elevated reaction temperature for the shortest practical closed and moderate heat is applied to the reaction vessel time, thereby minimizing thermal decomposition or unde while continuing the agitation. Thereupon, an exothermic 40 sirable side reactions. reaction ensues and upon reaching the desired reaction It has been found that by increasing the ratio of the temperature, cooling is provided through a jacket in the organo aluminum reactant to solvent that, other condi autoclave. In contrast to other processes for the manufac tions remaining constant, the yield is significantly im ture of tetraethylead, when this invention is employed it proved. Thus, when employing an aromatic solvent, in is not necessary to provide expensive and complex reflux creasing the molar ratio of organo aluminum to solvent equipment as, by proper choice of the carrier liquid, the ten fold in the reaction with a lead halide, a 200 percent reaction can be conducted in a closed system. Thus, increase in yield of organolead is obtained. Thus, by tetraethyllead can be produced without the co-presence increasing the molar ratio of organo aluminum reactant of ethyl chloride in the closed vessel. This greatly facili to solvent from .01 to .05, the conversion based upon lead tates control of the reaction and prevents the existence halide is increased from 12 percent to 17 percent. Sim of an otherwise hazardous operation. After completion ilarly, at a higher concentration a corresponding conver of the reaction, the organolead compound produced is sion increase is obtained. . in solution in the carrier liquid and the other products, While it has been found that in general any inert liquid namely the aluminum salt and metallic lead, can be re which acts as a solvent for the organo aluminum com moved by filtration and the organolead compound re 5 5 pound can be employed with good results, generally su moved from the carrier by distillation. perior results are obtained when aromatic hydrocarbon The operation described above can be varied and it solvents are employed. Not only is a more rapid reac-, is not intended that this invention be limited to the spe tion encountered, but the ultimate yield is considerably cific sequence of addition of the reactants. For example, improved in comparison, for example, to a parrafinic the organo aluminum compound can be added to a sus 60 hydrocarbon solvent. Among such preferred aromatic pension offinely divided lead halide with agitation. Other solvents are included benzene, toluene, xylene, and the modifications will be evident. liquid alkyl naphthalenes such as ov-methyl naphthalene, While the above operations were discussed in connec f3-methyl naphthalene, ethyl naphthalene, tetralim and tion with a batch operation, they can be successfully the like. adapted to a continuous process. In addition to apply The group III. A metallo organic compound employe ing the above operations to a continuous process, other in the process of this invention can be prepared by . modifications of a continuous process can be made, such methods well known in the art. For example, reaction as first mixing together all the reaction materials and between organo lithium compounds and aluminum halides then passing them continuously through a suitable reac produces the corresponding organo aluminum compound. tion zone. Thus, aluminum triethyl can be prepared by reaction be-, It has been indicated that the process of the present tween lithium ethyl and aluminum chloride. More re invention is conducted in the presence of an inert car cently, it has been proposed to produce organo aluminum. rier liquid. Hydrocarbons of appropriate boiling point : compounds by reaction between aluminum hydride and, with respect to the organolead compound produced are the appropriate olefin. It is not intended, however, that. satisfactory and can be chosen so as to provide a solution 75 the scope of this invention be limited to any particular ,

5 6 method of producing the hydrocarbon carrying reactant. what higher temperatures. Thus, if such means are pro This invention can be further understood by the follow vided, the process can be conducted successfully in the ing detailed working example of one method of practicing temperature range of between about -10 C. and 100 C. this invention as directed to the manufacture of tetra Conversely, in a batch operation, higher temperatures can ethyllead. likewise be employed if provision is made for chemically - . Example. I removing the aluminum halide produced from the locus of the organolead compound. Thus, with the more stable An autoclave equipped with internal agitation, external organo aluminum compounds, polar solvents can be co heating means, and external cooling means is employed employed or complexing agents having atoms capable having a hopper attached thereto for containing finely O of coordinating with the aluminum halide produced can divided lead salt. The hopper has a plugcock at the dis be successfully employed to provide successful reactions charge end for admission of the lead salt to the auto at more elevated temperatures. clave. To the autoclave are added 87 parts of toluene, While it was indicated above that, in general, a catalyst agitation is commenced and 3.9 parts of lead chloride is not required for the practice of this invention, certain of particle size of less than As inch were admitted to the 5 materials do exhibit a catalytic effect upon the reaction autoclave. The stop cock of the hopper was closed. The and, in many instances, their inclusion in the reaction autoclave is purged with dry nitrogen gas then 1.5 parts provides a smoother operation. Typical of such materials of triethyl aluminum are fed thereto. The reaction mix are heavy metal iodides as well as iodine itself, organic ture, while under a nitrogen atmosphere, was maintained iodides, certain ketones such as acetone and methyl ethyl between 20 and 25 C. for a total reaction period of /2 ketone, and ethers, amines, and aromatic solvents as in hour. The mixture was then filtered to remove solid dicated heretofore. constituents which are further processed for recovery of The following detailed examples serve to illustrate ad lead value. The filtrate was washed with an equal volume ditional specific embodiments of the present invention. of water. The organic layer was transferred to a still for However, the invention is not intended to be limited removal by vacuum distillation of the toluene and re 25 thereto. covery of the tetraethylead from the mixture. The con version obtained was 46 percent of the theoretical. Example II Similarly, when trimethyl aluminum, tripropyl alumi Following the procedure of Example I, with the excep num, triphenyl aluminum, tribenzyl aluminum, triethyl tion that the autoclave was sealed after adding the re aluminum, and tributyl aluminum are employed in the 30 actants, 1.5 parts of triethyl aluminum were reacted with process of the foregoing example, satisfactory yields of 4.0 parts of lead bromide in 100 parts of n-hexane. The tetramethyllead, tetrapropyllead, tetraphenylead, tetra temperature employed was 80 to 89 C. and the reaction benzyl lead, tetraethylead, and tetrabutyllead are pro period was one hour. Based upon lead bromide converted duced, respectively. Likewise, when trimethyl boron, to organolead, a nearly quantitative yield of tetraethyllead tripropyl gallium, triphenyl indium, tribenzyl gallium, 35 was obtained. triethyl boron, and tributyl indium are employed in the Example III process of the foregoing example, satisfactory yields of In a reactor maintained under an atmosphere of dry tetramethylead, tetrapropyllead, tetraphenylead, tetra nitrogen, 1.5 parts of triethyl aluminum were reacted benzyllead, tetraethylead, and tetrabutyllead are pro with 3.91 parts of lead chloride in 200 parts of n-hexane. duced, respetcively. 40 Room temperature was employed and a spontaneous re In general, the reaction of this process is completed action occurred. Tetraethylead was recovered in high within a relatively short period at elevated temperatures, yield. but a somewhat longer time is required at lower tempera Example IV tures. In general, a reaction time of between about one half to twenty hours is employed. In particular, in the Tetrahexyllead is prepared in high yield by reacting tri manufacture of tetraethyllead with triethyl aluminum and hexyl aluminum with lead chloride in essentially stoichi lead bromide, we prefer to employ a reaction time of ometric amounts in the presence of cyclohexane at atmos about ten hours or less. pheric pressure and at a temperature of 75 to 85 C. for The pressure employed in the reaction vessel is not three hours reaction time. critical and is usually the autogenous pressure created 50 Example V by the carrier liquid at the temperature employed. Since organolead compounds are relatively toxic, it is desirable Again employing the procedure of Example I, tetra to employe a closed vessel in conducting this reaction phenyl lead is obtained in high yield when triphenyl alu which may create an elevated pressure if low boiling minum dissolved in benzene is reacted with lead chloride carrier liquids are employed. 55 in essentially stoichiometric quantities. The temperature The temperature required in the operation of the proc employed is 75 to 83° C. for a period of 5% hours. ess of this invention depends to a large degree upon Example VI the nature of the products formed. It has been found Example I is repeated essentially as described with the that when elevated temperatures are employed, the alu 60 exception that tetraethylead is employed as the diluent minum halide produced in the reaction destroys the and the reaction temperature is 30 to 40 C. In this in organolead compound produced at a rate competitive stance, the process is conducted continuously by continu with the formation of the organolead compound. There ously feeding the triethyl aluminum and lead chloride to fore, in a batch operation wherein the contact time is the reactor and withdrawing a slurry of solids in tetra relatively extended, it is preferred to maintain the reac 65 ethylead from the reactor leaving a heel of tetraethylead tion temperature between about -10 C. to about 30° C. sufficient to maintain fluidity of the reaction mixture. Within this range, variation is possible depending upon Equally good results are obtained when the correspond the stability of the organolead compound produced, the ing and other organo compounds of gallium, boron and degree of dilution by the inert diluent, and duration of indium are employed in the above examples. For exam the reaction period. In a continuous operation wherein 70 ple, triethyl gallium, indium or boron can be reacted with the reaction products can be rapidly removed from the lead chloride to produce tetraethyllead. Triphenyl galli reaction zone or wherein a quenching operation can be um, indium or boron, preferably dissolved in a suitable employed so as to rapidly reduce the temperature of the solvent such as benzene can be reacted with lead bromide reaction mixture or to destroy the aluminum halide pro to produce tetraphenylead. Other examples will be evi duced, successful operation can be obtained with some is dent. 2,859,228 7 8 ... A particularly advantageous. and preferred method of with a trialkyl aluminum compound wherein each alkyl utilizing the process of this invention as specifically, di radical contains up to 8 carbon atoms inclusive...... rected to a commercial method of manufacturing tetras 3.A. process; for the manufacture of tetraethyl lead ethylead comprises starting with free aluminum and hy which comprises reacting lead chloride with triethyl alur driding to produce the corresponding aluminum hydride 5. minum. - ...... as the first stage. A second stage then comprises reacting 4. The process of claim 3: wherein the reaction is con said hydride with ethylene preferably in the presence of a ducted in the presence of an inert carrier liquid. solvent suitable as a carrier for the ethyl aluminum, which 5. The process of claim 3 wherein the reaction is con is thereafter reacted with the lead chloride in accordance ducted at a temperature between about -10 to 100. C. with the foregoing description of the present invention. l0. 6. The process of claim 5 wherein the reaction is con We claim: ...... ducted in the presence of an inert carrier liquid. 1. A process for the manufacture of hydrocarbon lead 7. The process of claim 5 wherein said carrier liquidis compounds which comprises reacting a hydrocarbon me toluene. - ...... tallic group III-A compound wherein each hydrocarbon radical has up to about 10 carbon atoms inclusive and is 5. References Cited in the file of this patent selected from the group consisting of alkyl and aryl radi cals with a lead halide of a halogen selected from the UNITED STATES PATENTS : ... group consisting of chlorine, bromine and iodine. . . . 2,786,860 Ziegleret al.------Mar. 26, 1957 2. A process for making alkyllead compounds which OTHER REFERENCES... . . comprises reacting a lead halide of a halogen selected from 20 Leeper, et al., Chem. Revs. 54, 108 (1954) citing Austin the group consisting of chlorine, bromine, and iodine et al. J. A. C. S. 54, 3726 (1932). ..