US2838556A - Organo-aluminum compounds - Google Patents

Description

United States Patent ORGANO-ALUMINUM COMPOUNDS Delmer L. Cottle, Highland lark, and Stanley B. Mirviss,

Roselle, N. 1., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Application October 27, 1955 Serial No. 543,257

16 Claims. (11. 260-448) This invention relates to ogano-aluminum compounds and more particularly relates to an improved method for reducing organo-aluminum halides to form organo-aluminum compounds containing a greater proportion of organic substituents.

Organo-aluminum compounds have been reduced here-.

a number of disadvantages. For example, these reduc-.

ing reactions are strongly exothermic and, as a result,

proper control of the reaction is extremely difficult. Also,

when sodium, for example, is employed as the reducing metal, it is necessarythat the sodium be completely reacted for safety reasons, since otherwise the operator must dispose of thisihighly reactive metal at the end of the preparation. Another disadvantage is that the reducing metal employed in the reaction must be broken up into a finely divided state if it is to react completely in the preparation. For these reasons, there has been a need for a simple, safe and effective method for reducing organo-aluminum compounds, particularly since these reduced organo-aluminum compounds are finding increasinguse as catalysts for carrying out chemical reactions.

A novel and improved method has now been found for converting organo-aluminum halides to organo-aluminum compounds containing ahigher substituents. More specifically, the improved method of the present invention comprises reacting an organoaluminum halide with'the reducing metalin the form of an amalgam, preferably in the form of a liquid amalgam. It has been found that this improved method promotes a readily controllable reaction which can be carried out safely without danger to the operator. The present method also has the advantage that it can be carried out con-v veniently on either a batch or continuous basis. The use ofliquid amalgam is particularly convenient.

The reducing metals useful in the method of the present invention are preferably alkali metals such as, for example, sodium, potassium and lithium. If desired, alkaline earth metals such as calcium, strontium and barium may also be employed. The amalgams are prepared simply by mixingthe reducing metal with mercury. Generally it will be preferable to mix the maximum amount of reducing metal with mercury which will still provide an amalgam which willbe liquid at the temperature of reaction and preferably which is also llquld at room temperature. Lesser amounts of the reducing metal may be employed if desired, although this will necessitate the use of greater amounts of amalgam in the proportion of organic.

2 reaction with the organo-aluminum halides. The maximum amount of the reducing metal which may be incorporated in the amalgam and still provide a liquid amalgam will depend upon the particular metal selected. For example, when using sodium metal, liquid amalgams containing up to about 1.5 weight percent, based on total amalgam, can be employed. At concentrations much above about 1.5 weight'percent of sodium, the amalgam is a solid at the temperature of reaction with the organo-aluminum halides and thus suffers the disadvantage of failing to provide effective contacting be- A tween the sodium and the organo-aluminum halide. Con

centrations as low as about 0.1 weight percent or lower of the reducing metal may be employed if desired. It will be understood, of course, that amalgams containing mixtures of two or more reducing metals may be employed in the present method if desired. The presence of the mercury in the reaction mixture does not interfere with the present reaction as it is inert.

The organo-aluminum halides which may be reduced in accordance with the improved method of the present invention include (1) diorgano-aluminum monohalides having the formula R AlX and (2) monoorgano-aluminum dihalides having the formula RAlX and (3) mixtures of diorgano-aluminum monohalides and monoorgano-aluminum dihalides. In the above formulas,

been found that excellent results have been obtained when R represents an ethyl group. R may also represent various other organic groups such as, for example, aryl (e. g.'phenyl), aralkyl and alkaryl groups. In the above formulas, X represents a halogen atom. The present method is particularly effective with organo-aluminum halides wherein X represents a bromine, iodine and especially a chlorine atom. It will be understood that two halogen atoms in the dihalides may be different halo gens. Specific examples of diorgano-aluminum monohalides useful in the present invention include diethyl aluminum chloride, dimethyl aluminum chloride, diethyl aluminum bromide, dimethyl aluminum bromide, diethyl aluminum iodide, dimethyl aluminum iodide, dipropyl aluminum chloride, dibutyl aluminum bromide, methyl ethyl aluminum chloride, diphenyl aluminum bromide, phenyl ethyl aluminum chloride, etc. Specific examples of monoorgano-aluminum dihalides which may be employed in the present invention include ethyl aluminum dichloride, ethyl aluminum dibromide, ethyl aluminum diiodide, methyl aluminum dichloride, butyl aluminum dibromide, propyl aluminum diiodide, ethyl aluminum chloride bromide, phenyl aluminum dichloride, etc.

The present invention is also applicable to organoaluminum sesquihalides which are mixtures of diorganoaluminum monohalides and monoorgano-aluminum dihalides. These sesquichlorides may be prepared in accordance with the following chemical equation:

organo-aluminum halide and the monoaluminum dihalide,

Patented June 10, 1958.

Specific examples of these'organo-aluminum sesquihalides include ethyl aluminum sesquichloride, ethyl aluminum sesquibromide, ethyl aluminum sesquiiodide, methyl aluminum sesquichloride, etc. Other mixtures of the monohalides and dihalides in any proportions may also" beemployed in this invention.

The present method is carried out simply by contacting- (wherein for simplicity the reducing metal is shown as sodium metal):

Thus in carrying out the present method, approximately stoichiometric proportions of the reactants will be employed and the particular stoichiometric proportions will depend upon the organo-aluminum halide to be reduced and the organo-aluminum compound to be formed as indicated by the above chemical equations. The aluminum metal which is a byproduct of the reaction. is produced in a finely divided form which does not interfere with the reaction.

Generally the present reducing reaction will be carried out at a temperature in the range of about 80 to 180 (3., preferably in the range of about 100 to 160 C. It is particularly preferred when reducing a monorgano-alu-minum dihalide to a diorgano-aluminum monohalide to employ temperatures in the range of about 100 to 140 C., e. g., 120 C. It is also particularly preferred when reducing a diorgano-aluminum monohalide to a triorganoaluminum to employ reaction temperatures in the range of about 140 to 160 C., e. -g., 150 C. The time required to effect the desired reduction will generally be in the range of about 0.1 to 10 hours, usually in the range of about 0.5 to hours. Quite effective results have been obtained employing a reaction time in the range of about 1 to 3 hours. Generally it will be convenient to carry out the present reaction at atmospheric pressure although if desired somewhat higher or lower pressures may be used. Also, if desired, the reducing metal may be added incrementally duringthe reaction. The incrementally-added reducing metal reacts almost instantaneously with the mercury present on mixing to form an amalgam rather than participating in the organo-aluminum halide reduction. The incremental addition of the reducing metal can be employed with particular advantage when the present invention is employed ina continuous process.

After the reaction is'completed, the resultant organoaluminum product (i. e., the diorgano-aluminum monohalide formed from a monoorgano-aluminum dihalide; or the triorgano-aluminum formed from monoorganoaluminum dihalide and/or diorgano-aluminum monohalide) may be separated from the reaction mixture. This may be accomplished, for example, by vacuum distillation or by extraction using an organic solvent. Vacuum distillation is usually preferred and generally will be carried out at a pressure in the range of about 0.1 to 150, preferably about 1 to 100, mm. of Hg. Preferablythe temperature during vacuum distillation is maintained inthe range of about 30 to 200 C., more preferably in the range of about 70 to 160 C. In the alternative extraction method, the organo-aluminum product is extracted usingv Preferred solvents are saturated aliphatic hydrocarbons containing about 5 to 10 carbon atoms. The saturated aliphatic hydrocarbon solvents are particularly preferred when recovering alkyl aluminum products from the reaction mixture. Preferably the organic solvent is relatively low boiling so that the organo-aluminum product may be recovered simply by evaporation or stripping off the solvent. Specific examples of organic solvents useful in the recovery of the organo-aluminum products include petroleum ether, a mixture of hexanes or heptanes, n-heptane, isooctane, benzene, toluene, diethyl ether, diisopropyl ether, di-n-butyl ether and the like.

The invention will be more fully understood by reference to the following examples. It is pointed out, however, that the examples are given for the purpose of illustration only and are not to be construed as limiting the scope of the present invention in any way. These examples illustrate the reduction of ethyl aluminum halide using sodium metal as the reducing metal in the form of a liquidzamalgam in accordance with the present invention, the reaction resulting. in the conversion of the alkyl aluminum halide to a more highly alkylated aluminum compound, or expressing in another way, resulting in the dehalogenation of the alkyl aluminum halide.

Example I 1 gram atomic weight (23 grams) of sodium was converted to a 1 weight percent of sodium amalgam by adding small pieces of the sodium metal to 5 pounds of mercury While stirring continuously in a flask protected by a nitrogen atmosphere. T 0 this liquid sodium amalgam was added 106 grams of a mixture containing 82 weight percent diethyl aluminum chloride and 18 weight percent ethyl aluminum dichloride. The heat of reaction raised the temperature of the reaction mixture from room temperature to about 48 C. The mixture was further heated with stirring to about 120 C. and held there for aboutl hour and 25 minutes. The product was distilled directly from the reaction mixture at a pressure of 3 mm. of Hg and then redistilled at a pressure of about 3 mm. of Hg to give a final product yield of 66 grams. The product was found to contain about 68 weight percent of diethyl aluminum chloride and about 32 weight percent of triethyl aluminum.

Example 11 Example Iwas'repeated except that the reaction mixture was heated to 143150 C. for about 1 hour and 40 minutes. A yield of 48 grams of product was obtained from the resultant reaction mixture by vacuum distillation at 83 C. at 3 mm. of Hg. This product contained about 96.7 weight percent of triethyl aluminum and about 3.3 weight percent of diethyl aluminum chloride.

EXAMPLE III In this example, 173 grams of a mixture containing 82 weight percent of diethyl-aluminum chloride and 18 weight percent of ethyl aluminum dichloride, and 91 grams of a mixture of 41 weight percent of diethyl aluminum bromide and 59 weight percent of ethyl aluminum dibromide, were added to a stirred amalgam containing about 1.2 weight percent of sodium (the liquid amalgam contained 54.4 grams of sodium metal). During the addition of the 'alkyl aluminumhalide mixture, the temperature of the-reaction mixture rose from 70 C. to 142 C. The temperature was maintained'at 142154 C. for a period of 2 hours and 10 minutes. A yield of 112 ml. of product was obtained from the reaction mixture by vacuum distillation at 8083 C. at 3 mm. of Hg. This product contained about 1.6 weight percent of diethyl aluminum chloride and about 98.4 weight percent of triethyl aluminum.

EXAMPLE IV Inthis example, 2.56 gram atoms (59 grams) of sodiumv were converted into the formv of'a liquid amalgam containing. 1.3 weight percent of sodium metal by the grams of sodium metal was added to the spent amal-v gam in the reaction flask followed by the addition of 145 grams of fresh ethyl aluminum chloride (84 weight percent of diethyl aluminum chloride and 16 weight percent ethyl aluminum dichloride). The'reaction mixture was then heated for 2 hours at l43l50 C., after which the product was distilled directly from the reaction flask and redistilled at about 80-83 C. at 3 mm. of Hg. A yield of 234 ml. of product was obtained which contained no detectable amount of ethyl aluminum halide.

EXAMPLE V In this example, sodium metal was added to pounds of mercury to make a liquid sodium amalgam containing 1.07 weight percent of sodium metal. To this liquid amalgam was added with stirring 251 grams of analytically pure diethyl aluminum chloride. The temperature of the liquid amalgam was 75 C. at the start of addition and at the end of 12 minutes, during which the entire amount of diethyl aluminum chloride was added, the temperature had dropped to 68 C. The resultant mixture was then heated to 150 C. and held there for about 2 hours. The product was distilled directly from the reaction mixture at a pressure of 3 mm. of Hg and then redistilled at a pressure of 3 mm. of Hg. The resultant product had a boiling point of 80-835 C. with 95 weight percent of the product distilling from 82 to 832 C. A nearly quantitative yield of aluminum triethyl was obtained which contained lessv than 0.5 weight percent of diethyl aluminum chloride.

EXAMPLE VI 1 gram atomic weight (23 grams) of sodium metal was added to mercury to form a liquid amalgam containing 1 weight percent of sodium metal. This liquid amalgam was treated dropwise while stirring with 145 grams of ethyl aluminum sesquichloride (which contained 45 weight percent diethyl aluminum chloride and 55 weight percent ethyl aluminum dichloride). The heat of reaction carried the temperature from room temperature to about 58 C. The reaction was further heated and a mildly exothermic reaction took place, raising the temperature to 118 C. The final reaction temperature at the end of 45 minutes was 98 C. Distillation at a pressure of 3 mm. of Hg directly from the reaction mixture and redistillation gave 80 cc. of a product boiling at 69-80 C. The product analyzed as 93 weight percent diethyl aluminum chloride. The remainder of the distillate appeared to be aluminum triethyl.

What is claimed is:

1. In a method wherein an organo-aluminum halide containing a hydrocarbon radical of 1 to 12 carbon atoms selected from the group consisting of alkyl and phenyl groups is reduced with a reducing metal selected from the group consisting of alkali metals and alkaline earth metals, the improvement which comprises carrying out said reduction with a liquid amalgam of said reducing metal.

2. Method according to claim 1 wherein said reducing 4. Method according to claim 3 wherein said alkyl aluminum halide is an ethyl aluminum chloride.

5. Method according to claim 4 wherein said alkyl aluminum halide comprises ethyl aluminum dichloride.

6. Method according to claim 4 wherein said alkyl aluminum halide comprises diethyl aluminum chloride.

7. Method according to claim 4 wherein said alkyl aluminum halide comprises ethyl aluminum sesquichloride.

8. Method according to claim 1 wherein said organoaluminum halide is a diphenyl aluminum halide.

9. In a method for reducing a C to C alkyl aluminum chloride by reaction with sodium metal, the improvement which comprises carrying out said reaction with a liquid amalgam containing 0.1 to 1.5% by weight of said sodium metal.

10. An improved method for converting a C to C alkyl aluminum halide to a more highly alkylated aluminum compound which comprises reacting said alkyl aluminum halide with a liquid amalgam containing 0.1 to 1.5 by weight of sodium at a temperature of about to 180 C. for about 0.1 to 10 hours, and then separating the more highly alkylated aluminum compound from the reaction mixture.

11. Method according to claim 10 wherein said alkyl aluminum halide is an ethyl aluminum chloride.

12. Method according to claim 10 wherein said separation is carried out by vacuum distillation.

13. Method according to claim 10 wherein said separation is carried out by extracting the resultant more highly alkylated aluminum compound into an organic solvent.

14. An improved method for converting ethyl aluminum dichloride to diethyl aluminum chloride which comprises reacting ethyl aluminum dichloride with sodium metal in the molar ratio of about 2:3, at a temperature of about to C. for about 0.5 to 5 hours, said sodium metal being in the form of a liquid amalgam containing about 0.1 to 1.5 by weight of said sodium metal, and then separating the diethyl aluminum chloride from the resultant reaction mixture by vacuum distillation.

15. An improved method for converting diethyl aluminum chloride to triethyl aluminum which comprises reacting ethyl aluminum dichloride with sodium metal in the molar ratio of about 1:1, at a temperature of about 100 to 160 C. for about 0.5 to 5 hours, said sodium metal being in the form of a liquid amalgam containing about 0.1 to 1.5 by weight of said sodium metal, and then separating the triethyl aluminum from the resultant reaction mixture by vacuum distillation.

16. An improved method for converting ethyl aluminum dichloride to triethyl aluminum which comprises reacting ethyl aluminum dichloride with sodium metal in the molar ratio of about 1:2, at a temperature of about 100 to 160 C. for about 0.5 to 5 hours, said sodium metal being in the form of a liquid amalgam containing about 0.1 to 1.5 by weight of said sodium metal, and then separating the triethyl aluminum from the resultant reaction mixture by vacuum distillation.

References Cited in the file of this patent UNITED STATES PATENTS Ziegler Oct. 12, 1954 OTHER REFERENCES

Claims (2)

1. IN A METHOD WHEREIN AN ORGANO-ALUMINUM HALIDE CONTAINING A HYDROCARBON RADICAL OF 1 TO 12 CARBON ATOMS SELECTED FROM THE GROUP CONSISTING OF ALKYL AND PHENYL GROUPS IS REDUCED WITH A REDUCING METAL SELECTED FROM THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID REDUCTION WITH A LIQUID AMALGAM OF SAID REDUCING METAL.

9. IN A METHOD FOR REDUCING A C1 TO 12 ALKYL ALUMINUM CHLORIDE BY REACTION WITH SODIUM METAL, THE IMPROVEMENT WHICH COMPRISES CARRYING OUT SAID REACTION WITH A LIQUID AMALGAM CONTAINING 0.1 TO 1.5% BY WEIGHT OF SAID SODIUM METAL.