REACTIONS BETWEEN ORGANOLEAD COMPOUNDS AND SOME

Organolead Compounds. Robert W. Leeper , Lawrence Summers , and Henry Gilman. Chemical Reviews 1954 54 (1), 101-167. Abstract | PDF | PDF w/ Links...
3 downloads 0 Views 513KB Size
Download PDF
[CONTRIBUTION FROM THE CHEMICAL

LABORATORY OF IOWA STATE

COLLEGE]

REACTIONS BETWEEN ORGANOLEAD COMPOUNDS AND SOME METALLIC HALIDES HENRY G I L M A N

AND

L. D. A P P E R S O N

Received January 30, 1939 INTRODUCTION

Incidental to studies on the low-temperature formation of free radicals from organometallic compounds, it was desirable to determine the effect of some metallic halides (particularly, aluminum chloride) on different types of organolead compounds. Phenyllead compounds and aluminum chloride.-The essential reactions in petroleum ether (b.p., 90-115') or hexane appear to be the following:

+

+ + +

(CJIb)4Pb AlCls -+ ( C J ~ K ) ~ P ~ C dI I ~ A l c l.~. . . . . , .[I1 (CJIs)rPb CSHKAICI~ .--) (cdI~)sPbC1 ( C ~ H S ) ~ A. ~. .C. [11] ~. (CdIs)sPbCl AICIs -+ (Cs&)zPbC12 CeHaAlCIz. . . . . . [111]

+

+

No biphenyl, chlorobenzene, or lead dichloride were isolated. The reaction is halted at the diphenyllead dichloride stage, and this compound was shown to be unaffected when treated separately with aluminum chloride. The phenylaluminum chlorides [(C0Hs)eAICl and COHEAICIZ]are undoubtedly in an equilibrium mixture, and this equilibrium may include triphenylaluminum a t elevated temperatures. The organoaluminum compounds were qualitatively analyzed by the color test'", and semi-quantitatively determined both by measuring the benzophenone resulting after treatment with benzoyl chloride,Iband by the formation of R H compounds by hydrolysis. Under the experimental conditions followed, there is no reaction of benzoyl chloride with tetraphenyllead, triphenyllead chloride and diphenyllead dichloride. The triphenyllead chloride and diphenyllead dichloride may owe their formation to reactions other than those indicated in I, 11,and 111. Austin2 has shown that triphenyllead chloride is converted, by heating in butyl alcohol for six hours, to diphenyllead dichloride and tetraphenyllead in about 10 per cent. yields. Under our more moderate conditions, the 1 ( a ) GILMAN AND SCHULZE, J . Am. Chem. SOC., 47, 2002 (1925). (a) Other studies have shown that acid halides are suitable reagents for characterizing organoaluminum compounds. 162

ORGANOLEAD COMPOUNDS AND METALLIC HALIDES

163

triphenyllead chloride was shown to be essentially unaffected. Accordingly, the diphenyllead dichloride isolated from our cleavage experiments is not due to pyrolysis. There is a possibility that some of our triphenyllead chloride may have resulted from interaction of tetraphenyllead and diphenyllead dichloride. However, here, too, our conditions were more moderate than those used by Austin2for this particular reaction. Furthermore, it is highly probable on theoretical grounds that the reaction proceeds stepwise, and that triphenyllead chloride is a precursor of diphenyllead dichloride in the cleavage reactions. Finally, we have shown that a 75 per cent. yield of diphenyllead dichloride is obtained from triphenyllead chloride and aluminum chloride. Ethyllead compounds and aluminum chloride.-The first reactions of tetraethyllead are like reactions I and I1 shown by tetraphenyllead. Also it is quite likely that a reaction like I11 occurs, even though diethyllead dichloride is not isolated. What very probably happens is that diethyllead dichloride is formed, and then breaks down in accordance with the following transformations, reaction IV predominatinga

+ PbClz + CaHsCl. . . . . . .[IV] + PbClz + 2CZHs.. . . . . . . . . . . . . . [VI

2(CzHa)zPbClz + (CZHa)3PbCl

(C&&PbC12 We have found that the yields of lead chloride and ethyl chloride increase when the ratio of aluminum chloride to tetraethyllead is increased. Under such conditions, one would not expect to find any significant quantity of triethyllead chloride because this compound with aluminum chloride gives the relatively unstable diethyllead dichloride, in accordance with reaction 111. This agrees with our observation on the reaction between diethyllead dichloride and aluminum chloride. Incidental to the formation of ethyl chloride, it is significant that small quantities of hexaethylbenzene were isolated when benzene was used as the reaction medium. Of course, this Friedel-Crafts reaction product may have come from the disproportionation of ethyl radicals (reaction V) to ethylene. Reaction IV has been shown recently to be the predominant reaction when solid di-n-butyllead dichloride was heated a t 130' for one-half hour'*. Evidence was obtained earlierabfor both reactions IV and V when solid diethyllead dibromide was allowed to decompose spontaneously a t room temperatures or heated at 100'.

* AUSTIN,ibid.,

64, 3287 (1932). EVANS,J . Chem. Soc., 1898, 1466. (a) Unpublished communication by Dr. George Calingaert, Regional A.C.S. Meeting, Columbus, Ohio, Nov. 1937. There is a possibility that the RzPbX2 compounds may be converted to RPbXs types, by aluminum chloride or otherwise, and that the RPbX, compound8 then PbX2. For a general account of RPbXs types see LBSBBPI, decompose to RX Compt. rend., 200,669 (1935);204,1822 (1937). a (a)

+

164

HENRY GILMAN AND L. D. APPERSON

The organoaluminum compounds formed were chiefly diethylaluminum chloride and ethylaluminum dichloride, together with occasional small quantities of triethylaluminum. These ethylaluminum compounds appeared to form complexes with the various ethyllead compounds, and the complexes were broken up by hydrolysis, by distillation, or by reaction with acyl halides. The mixture of diethylaluminum chloride and ethylaluminum dichloride (prepared both by the reaction of aluminum with ethyl chloride, and the reaction of aluminum chloride with triethylaluminum) cleaved tetraethyllead [11]and triethyllead chloride. The cleavage of triethyllead chloride was effected by heating the solid reactants to 150°, but no cleavage took place under the milder conditions when ether or petroleum ether was used as a medium. Tetraethyllead and other inorganic halides.-Anhydrous ferric chloride is reduced promptly to ferrous chloride, which was obtained in a high state of purity and in excellent yield. Chloroplatinic acid was reduced immediately to platinum, and bismuth chloride gave ethylbismuth compounds. The other reaction products were ethyllead chlorides and lead chloride. The literature contains accounts of earlier reactions of organolead compounds with metallic halides. Browne and Reidk reported a vigorous reaction between tetraethyllead and aluminum chloride to give triethyllead chloride and an unidentified gas. With silicon tetrachloride they obtained triethyllead chloride; and titanium tetrachloride was reduced by tetraethyllead. Goddard and co-workers treated tetraphenyllead with the halides of arsenic, antimony, bismuth, tellurium, and tin, to obtain in each case diphenyllead dihalide as well as the halides of the other RM compounds such as diphenylbismuth bromide.& Thallic chloride and tetraphenyllead gave diphenyllead dichloride and diphenylthallium chloride; and thallic chloride with triethyllead chloride gave diethyllead dichloride and thallous chloride.4c From reaction between thallic chloride and tri-m-xylyllead there resulted di-m-xylyllead dichloride and thallous chloride.4d Krause and S ~ h m i t obtained z~~ phenylmercuric chloride from triphenylethyllead and mercuric chloride; Kocheskov and Nesmeyanovu treated phenyllead compounds with mercuric chloride to obtain phenylmercuric chloride as a product wherever reaction occurred. These authors noted no reaction between diphenyllead dichloride and mercuric chloride in alcohol; but the same reactants with sodium hydroxide gave phenylmercuric chloride and lead dioxide. (a) BROWNE AND REID,J . Am. Chem. Soe., 49,830 (1937); (b) GODDARD, ASHLEY,

EVANS,J . Chem. SOC.,121, 978 (1922); (e) GODDARD AND GODDARD, ibid., 121, 260 (1922); ( d ) GODDARD, ibid., 123, 1172 (1923); (e) KRAUSEAND S~HMITZ, Ber., 62, 2159 (1919); (f) KOCHESKOV AND NESMEYANOV, ibid., 67, 317 (1934). We have also shown that ethylmercuric chloride is formed from tetraethyllead and mercuric chloride. AND

ORGANOLEAD COMPOUNDS AND METALLIC HALIDES

165

The experimental part describes some reactions of triaryllead compounds with aluminum chloride. EXPERIMENTAL

TetrGphenyllead and aluminum chloride.-A petroleum ether (100 cc.) suspension of 0.025 mole of tetraphenyllead and 0.1 mole of aluminum chloride was heated, with stirring, for 6 hours in a flask contained in a bath of boiling water. Nitrogen was used as the inert atmosphere. The practically colorless upper layer was separated from the yellowish lower, solid layer. The upper layer gave a weak positive color test'", and steam distillation yielded no chlorobenzene nor biphenyl. The lower solid layer yielded 26% of triphenyllead chloride, 46.5% of diphenyllead dichloride, and a small amount (2.5 g.) of tetraphenyllead. The diphenyllead dichloride waa characterized by conversion to tetraphenyllead by means of phenylmagnesium bromide. In another experiment under corresponding conditions, 0.03 mole of tetraphenyllead was cleaved by 0.025 mole of aluminum chloride. The products were triphenyllead chloride (60%), diphenyllead dichloride (39%) and a trace of tetraphenyllead. The phenylaluminum compounds were decomposed by the ammonium acetate solution used in working up the products. In order to characterize the phenylaluminum compounds, the reaction mixture from 0.027 mole of tetraphenyllead and 0.025 mole of aluminum chloride was cooled and treated with 0.025 mole of benzoyl chloride. After standing overnight, the mixture was hydrolyzed. In addition to the usual phenyllead compounds, there was isolated (as the oxime) a 40% yield of benzophenone. Triphenyllead chloride and aluminum chloride.-A mixture of 0.0175 mole of triphenyllead chloride and 0.020 mole of aluminum chloride in petroleum ether was heated for 6 hours in a bath containing boiling water. The yield of diphenyllead dichloride was 75%. Tetraethyllead and aluminum chloride.-To a hexane solution of 0.05 mole of tetraethyllead was added slowly, by means of a hopper, 0.05 mole of aluminum chloride. The reaction was slightly exothermic, and the mixture soon separated into two layers. After refluxing for one hour (during which time no gas was evolved), the mixture was hydrolyzed. The products isolated were 76% of triethyllead chloride and a trace of lead chloride. In a check run, the yield of triethyllead chloride was 83%. In other experiments, the upper layer was shown to contain some tetraethyllead, but to be free of aluminum. The lower layer was distilled directly under reduced pressure. The initial distillation proceeds quite slowly, and is accompanied by gas evolution incidental to some decomposition of ethyllead compounds even with the use of an efficient pump used to get low pressures in all the distillations made. Subsequent fractionations proceeded more smoothly. The several fractions were shown by analysis to contain ethylaluminum dichloride and lesser amounts of diethylaluminum chloride and triethylaluminum. It is known that a t room temperature ethylaluminum dichloride and triethylaluminum give diethylaluminum chloride. The organoaluminum compounds will be reported separately later. In another series of experiments in which the excess of aluminum chloride was progressively increased so that one mole equivalent of tetraethyllead was treated with two and three mole equivalents, respectively, of aluminum chloride, the products were triethyllead chloride, a greater amount of lead chloride, ethyl chloride, and ethylaluminum dichloride as the preponderant ethylaluminum product. From

166

HENRY OILMAN AND L. D. APPERSON

one reaction between 0.24 mole of tetraethyllead and 0.5 mole of aluminum chloride, the yields were 21% of triethyllead chloride, 9% of lead chloride, 56% of ethylaluminum dichloride and a trace of ethyl chloride. The ethylaluminum dichloride was characterized, in part, by the formation of propiophenone subsequent to reaction with benzoyl chloride, and by evolution of ethane on hydrolysis. When these reactions using an excess of aluminum chloride were carried out in benzene, there was always isolated small quantities of hexaethylbenzene (mixture melting point). From an experiment using three mole equivalents of aluminum chloride, the yields of lead compounds were: 15% of triethyllead chloride and 72% of lead chloride. The ethylaluminum compounds were characterized by both the color test and the preparation of propiophenone; and the ethyl chloride, isolated to the extent of about lo%, was characterized by first forming ethylmagnesium chloride and then using this Grignard reagent to prepare ethylmercury chloride (mixture melting point). Triethyllead chloride and aluminum chloride.-A mixture of 0.02 mole of triethyllead chloride and 0.02 mole of aluminum chloride in petroleum ether was warmed for one-half hour. Again, two layers formed: the upper layer gave a weak color test; the lower layer, on hydrolysis, yielded 63% of lead chloride and 38% of recovered triethyllead chloride. No diethyllead dichloride was isolated. Diethyllead dichloride and aluminum chloride.-A 72% yield of lead chloride and a 20% yield of triethyllead chloride were obtained from reaction, in petroleum ether, between 0.11 mole of diethyllead dichloride and 0.1 mole of aluminum chloride. From the evolved gases there was isolated about 15% of ethyl chloride, and a hydrocarbon mixture consisting of 7.2% of unsaturates and 30% of saturates. The saturated hydrocarbon mixture appears to consist largely of ethane. Triethyllead chloride with triethylaluminum, and with diethylaluminum chloride and ethylaluminum dichloride.-Triethyllead chloride dissolved exothermally in a hexane solution of triethylaluminum; and when most of the lead compound was added, there was a separation into two layers. Subsequent to hydrolysis, 75% of the triethyllead chloride was recovered. There was no evidence of lead chloride or diethyllead dichloride. There was no cleavage of triethyllead chloride by a mixture of diethylaluminum chloride and ethylaluminum dichloride when ether or petroleum ether were used as media. However, after heating the mixture of solids gradually to 150" there was isolated 10% of lead chloride, 30% of lead and about a 50% recovery of triethyllead chloride. No check experiment was made to determine how much of this reaction was due to simple pyrolysis. The mixture of ethylaluminum chlorides was prepared by direct action of ethyl chloride on aluminum turnings, using a crystal of iodine (or a few drops of ethyl iodide) as a catalyst. The aluminum, contained in a flask, was heated while ethyl chloride gas was admitted slowly and under a slight positive pressure6. Themixturewas heated by means of a hot plate until fuming began; thereafter, a water bath was used. When no more ethyl chloride was absorbed, as shown by the U-tube with mercurys, the light-brown solution was filtered and then distilled to give a colorless distillate (b.p., 63'/3 mm.). The mixture of ethylaluminum chlorides was also prepared by adding aluminum chloride to triethylaluminum. The mixture fumes, and often inflames, in the air. I t was derivatized by treatment with benzoyl chloride to give propiophenone. 6 For a related technique on the preparation of methyl- and ethylmagnesium chlorides, see GILMAN,ZOELLNER,SELBY, AND BOATNER,Rec. trav. chim., 64, 584 (1935).

ORGANOLEAD COMPOUNDS AND METALLIC HALIDES

167

The mixture of ethylaluminum chlorides wm prepared earlier by Hall and NashO~ from aluminum, aluminum chloride, and ethylene; and by Hnisda and Krausa from aluminum and ethyl chloride. Incidental t o the preparation of etherates of organoaluminum compounds, the mono-etherate of aluminum chloride' was prepared. The compound distils a t 108"/2-3 mm. and melts a t 34". Anal. Calc'd for AlClS.(C2H&O: C1, 51.4. Found: C1, 51.0, 51.2. Tetraethyllead with diethylaluminum chloride and ethylaluminum dichloride.-A mixture of tetraethyllead and the ethylaluminum chlorides in petroleum ether was heated just below reflux for one hour. Although there was no separation into layers in this case, there was the characteristic yellow color. From two experiments, the yields of triethyllead chloride were 60% and 56%, respectively. The effective cleavage agent in these experiments is probably ethylaluminum dichloride, for when relatively pure diethylaluminum chloride was used the yields of triethyllead chloride were only 5% and 3%, respectively. The triethylaluminum mentioned earlier may owe its formation to the following reaction: (CzHs)J'b (C2Hs)AlCl --t (CzHs)aPbCl (C2Hs)sAl Tetraethyllead and Group V I I I halides. [By M. Lichtenwalter1.-To a solution of 11.5 g. of anhydrous ferric chloride in 200 cc. of ether was added 20.6 g. of freshly distilled tetraethyllead. A slight warming occurred with the formation of a voluminous precipitate. The precipitate was extracted with boiling ether until free of organolead compounds (triethyllead chloride and diethyllead dichloride). The residue consisted of 9 g., or a 90% yield, of anhydrous ferrous chloride. Anal. Calc'd for FeC12: Fe, 44.1;C1, 55.9. Found: Fe, 44.02; C1, 56.0. Under corresponding conditions, tetraethyllead was found to be without action on ferrous iodide, ferrous chloride, cobaltous bromide, and nickelous bromide. Chloroplatinic acid was reduced immediately by tetraethyllead to metallic platinum. Tetraethyllead and bismuth chloride. [By H. L. Yablunky1.-To a stirred solution of 0.032 mole of anhydrous bismuth chloride in 20 cc. of ether was added dropwise 0.0294 mole of tetraethyllead. A yellow solid precipitated immediately and the ether refluxed. When refluxing was continued for 4.5hours, by the external application of heat, the solid turned white. When the solid was dried and exposed t o the air i t ignited spontaneously; this is characteristic of triethylbismuth and diethylbismuth chloride. In a second experiment, no solvent was used, and the mixture of 0.03 mole of tetraethyllead and 0.4 mole of bismuth chloride was heated between 100°-130" for two hours. Dense white fumes were evident and the reaction was vigorous. There was isolated 1.15 g. of triethyllead chloride and 5 g. of lead chloride. Heating at this temperature under atmospheric pressure, with or without an inert atmosphere, would destroy any triethylbismuth. The fuming was probably due to decomposition of the ethylbismuth compounds and not to tetraethyllead, for no fuming was noted when finely ground bismuth metal and tetraethyllead were heated between 100"-130" for 5 hours. The tetraethyllead was recovered quantitatively.

+

+

6 ( a ) HALLAND NASH,J . Inst. Petroleum Tech., 23, 679 (1933); ( b ) HNIZDA AND KRAUS,J . Am. Chem. Soc., 60, 2276 (1938). Also GROSSE,Abstracts, American Chemical Society, Dallas meeting, 1938, and Baltimore meeting, 1939. 7 FRANKFORTER AND DANIELS,J. Am. Chem. SOC., 37, 2560 (1915).

168

HENRY GILMAN AND L. D. APPERSON

Triphenyhad with aluminum chloride.-A mixture of 7 g. (0.016 mole) and 3 g. (0.0225mole) of aluminum chloride in 100 cc. of petroleum ether (b.p., 90-115') was heated, with stirring in an atmosphere of nitrogen, by means of a steam bath for six hours. Hydrolysis was effected by addition of water. The solid material was separated by filtration, and the filtrate was distilled under reduced pressure. The combined solids were extracted with ammonium acetate solution and filtered. The filtrate, after treatment with dichromate solution, gave a quantity of lead chromate equivalent to 2 g. (45%) of lead chloride. The residue from the ammonium acetate extraction was treated with boiling chloroform, and the resulting residue was 0.4 g. (5.8%) of diphenyllead dichloride. The chloroform solution was evaporated under reduced pressure, and the residue was dissolved in an excess of hot alcohol. Upon cooling 2.5 g. (30%) of tetraphenyllead was isolated. The mother liquor, upon evaporation, yielded 0.5 g. (6.6%) of triphenyllead chloride. In a corresponding experiment, but with an excess of triphenyllead, the products were 3.6 g. (44%) of tetraphenyllead and 2.1 g. (47%) of lead chloride. A color test was obtained from the petroleum ether solution indicating the presence of organoaluminum compounds. Hydrolysis of the entire reaction mixture gave benzene upon fractionation. Triphenyllead chloride and tripheny1aluminum.-A mixture of 4 g. (0.00845 mole) of triphenyllead chloride and an excess of triphenylaluminum (prepared from 0.034 mole of diphenylmercury and aluminum in xylene solution) was heated on a steam bath for six hours. A quantitative conversion to tetraphenyllead took place under these conditions. Tri-o-tolyllead and aluminum chloride.-A mixture of equivalent amounts (0.02 mole) of tri-o-tolyllead and aluminum chloride was heated on a steambath for four hours, during which time there was a separation into two layers. The upper layer gave no color test and did not react with benzoyl chloride. Hydrolysis of the lower layer yielded 2.2 g. (40%) of lead chloride, 4 g. (35%) of tetra-o-tolyllead and 2 g. (21%) of unchanged tri-o-tolyllead. In another experiment, the mixture was heated for six hours. The products isolated were 1.4 g. (13.5%) of tri-o-tolyllead chloride, 3.5 g. (30.5%) of tetra-o-tolyllead, and 2.5 g. (45%) of lead chloride. SUMMARY

The following cleavage reactions have been shown to take place with phenyl- and ethyllead compounds: R4Pb A1C13 -+ R3PbCl RA1Cl2; RAlClz RaPbCl RzAlC1; RaPbCl AlCla -+ RaPbClz RdPb RAlC12. With ethyllead compounds, the RzPbClz compound is not isolated, and the aluminum compounds accelerate its decomposition to lead chloride, ethyl chloride and disproportionation products of the ethyl radicals. Tetraethyllead reacts promptly with anhydrous ferric chloride to give excellent yields of ferrous chloride of high purity; with chloroplatinic acid to give platinum; and with bismuth chloride to give ethylbismuth compounds.

+

-+

+

+

+

+

+