Process for producing dialkylaluminum alkoxides

Abstract

A robust method for producing dialkylaluminum alkoxides from trialkylaluminum species and aluminum alkoxides is provided, which is carried out in a non-coordinating solvent. In certain embodiments, the reaction can be facilitated by using at least one static mixer.

Description

[Technical field]

[0001] This disclosure relates generally to methods for preparing dialkylaluminum alkoxides, such as dimethylaluminum isopropoxide. [Background technology]

[0002]

[0002] Dialkylaluminum alkoxides are useful as precursors in the deposition of aluminum oxide films. Current methodologies for producing such compounds, such as dimethylaluminum isopropoxide (CAS number 6063-89-4), involve the reaction of trialkylaluminum species with various alcohols at very low temperatures or the direct reaction of trialkylaluminum species with aluminum alkoxides.

[0003]

[0003] One difficulty in the synthesis of such compounds is the pyrophoric nature of the trialkylaluminum species and their relatively low boiling points. Furthermore, aluminum alkoxides such as aluminum isopropoxide are solids. The reaction of trialkylaluminum species such as trimethylaluminum with solid aluminum isopropoxide is even more problematic since the reaction is very exothermic and requires the slow addition of trimethylaluminum. Furthermore, the reaction mixture often shows little mixing and localized hot spots occur. Therefore, improved methods for the preparation of such materials suitable for scale-up to the kilogram scale would be of great interest. Summary of the Invention

[0004] In summary, the present disclosure provides a robust method for producing dialkylaluminum alkoxides, such as dimethylaluminum isopropoxide. In one embodiment, flow chemistry techniques are used in combination with at least one static mixer to provide good yields of the desired compound. In general, the present disclosure provides a process for producing a dialkylaluminum alkoxide of formula (I): (R)2Al-OR 1 (I) wherein each R is independently selected from a C1 to C8 alkyl group; 1 is a C1-C8 alkyl group. The present invention provides a method for producing a compound of the formula: The method includes: (i) a solution comprising a compound of formula (R)Al and a non-coordinating solvent; and (ii) a compound of formula Al(OR 1 3 or a compound of the formula HOR 1 and a solution comprising a non-coordinating solvent. [Brief description of the drawings]

[0005] [Figure 1]

[0005] A simplified flow diagram illustrating one embodiment of the operation of the present process is shown. Trialkylaluminum starting material (1) is combined with aluminum alkoxide (2) in at least one static mixer (3) and the reaction is allowed to proceed by flow reaction. The product (4) in a solvent is then recovered and purified. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006]

[0006] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally used in its sense including "and / or" unless the content clearly dictates otherwise.

[0007]

[0007] The term "about" generally refers to a range of numbers considered equivalent to a stated value (e.g., having the same function or result). In many cases, the term "about" may include numbers that are rounded to the nearest significant figure.

[0008] Numeric ranges expressed using endpoints include all numbers subsumed within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

[0009] In a first aspect, the present disclosure provides a compound of formula (I): (R)2Al-OR 1 (I) wherein each R is independently selected from a C1 to C8 alkyl group; 1 is a C1-C8 alkyl group. The present invention provides a method for producing a compound of the formula: The method comprises: (i) a solution comprising a compound of formula (R)Al and a non-coordinating solvent; and (ii) a compound of formula Al(OR 1 2.) mixing a solution comprising the compound of formula 3 and a non-coordinating solvent.

[0010] In this method, exemplary C1-C8 alkyl groups include straight-chain and branched alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and the like.

[0011] In certain embodiments, R and R 1 are independently selected from C1 to C4 alkyl groups.

[0012] In one embodiment, the compound of formula (I) is dimethylaluminum isopropoxide. The compound of formula (I) can be represented by the empirical formula (R)2Al-OR 1 However, it is known to exist as a dimer. That is, dimethylaluminum isopropoxide is expressed as follows: TIFF2025508223000002.tif48170

[0013] A non-coordinating solvent is a solvent that does not react with either the starting material, i.e., the trialkylaluminum species or aluminum alkoxide, or the product of formula (I). In one embodiment, the non-coordinating solvent has a maximum boiling point of about 95° C. at atmospheric pressure. Examples of non-coordinating solvents include hydrocarbons having 5 to 8 carbon atoms and certain aromatic compounds optionally substituted with C1 to C8 alkyl groups. Examples of non-coordinating solvents include n-pentane, isopentane, n-hexane, n-heptane, n-octane, cyclohexane, benzene, toluene, xylene, and mixtures thereof.

[0014] Representative compounds of formula (I) include those in which R and R1 are shown in Table 1 below. TIFF2025508223000003.tif255170

[0015] Starting material (R)Al and starting material Al(OR 1 )3 are each dissolved in such a non-coordinating solvent prior to the coupling reaction. Advantageously, the concentration of each is high enough to ensure a fast and facile reaction while balancing the ability to control the exothermic reaction. In certain embodiments, the starting materials are present in the non-coordinating solvent at a concentration of about 0.2 M to about 5.0 M. For example, a compound of formula (R)3Al is dissolved in the non-coordinating solvent at a concentration of about 0.5 to about 5.0 M. In some embodiments, a compound of formula Al(OR 1 In yet another embodiment, a compound of formula Al(OR)3 is dissolved in a non-coordinating solvent at a concentration of about 0.2 to about 4.0 M. 1 ) The compound of formula 3 is not dissolved in a non-coordinating solvent but is added as a pure liquid or as a pure substance in the liquid phase.

[0016] The following table shows the advantageous range in which flow reactors can be utilized to reduce reaction exotherms and process blockages. TIFF2025508223000004.tif104170

[0017] Starting material reactants R-Al and Al(OR1 ) 3 reacts readily when combined. Advantageously, the reaction is carried out at a temperature of about 10°C to about 95°C.

[0018]

[0018] Additionally, in one embodiment, one or more static mixers are utilized. When multiple mixers are used, the mixers can be connected in series to facilitate mixing and reaction of the starting materials. Such static mixers are widely available commercially, for example, from McMaster-Carr (www.mcmaster.com). In some embodiments, the mixing is performed at a temperature greater than about 10°C.

[0019] In another embodiment, the starting material of formula (R)3Al is distilled under atmospheric or reduced pressure prior to use. 1 ) The compound in step 3 is filtered prior to use.

[0020] In certain embodiments, the method is carried out at a temperature of about 5° C. to about 95° C., or about 10° C. to about 40° C. In this regard, the starting materials can be used at room temperature and the equipment is operated in the recited temperature range.

[0021] Once the product of formula (I) has been collected (such as (4) shown in FIG. 1), it may be further purified by distillation to remove the solvent.

[0022] In another embodiment, a compound of formula (I) can be prepared by reacting a compound of formula HOR with a solution comprising a compound of formula (R)3Al and a non-coordinating solvent. 1 In this regard, the compound of formula HOR may be prepared using a solution comprising the compound of formula HOR 1 Exemplary compounds include methanol, ethanol, n-propanol, isopropanol, and the like.

[0023]

[0023] The dialkylaluminum alkoxide compound of formula (I) has a certain amount of non-coordinating solvent remaining upon purification. Therefore, in a further aspect, the present disclosure provides a dialkylaluminum alkoxide compound of formula (I): (R)2Al-OR 1 (I) wherein each R is independently selected from a C1 to C8 alkyl group; 1 is a C1 to C8 alkyl group, comprising about 20 to about 2000 ppm of a non-coordinating solvent.

[0024] In some embodiments, the compound comprises a non-coordinating solvent from about 20 ppm to about 2000 ppm, from about 50 ppm to about 2000 ppm, from about 100 ppm to about 2000 ppm, from about 250 ppm to about 2000 ppm, from about 20 ppm to about 1500 ppm, from about 50 ppm to about 1500 ppm, from about 100 ppm to about 1500 ppm, from about 250 ppm to about 1500 ppm, from about 20 ppm to about 1000 ppm, from about 50 ppm to about 1000 ppm, from about 100 ppm to about 1000 ppm, from about 250 ppm to about 1000 ppm, and all ranges and subranges therebetween.

[0025] The process of the present invention overcomes many of the problems of the prior art processes, and the product of formula (I) has also been found to have superior purity. Thus, in a further aspect, the present disclosure provides a method for the preparation of a compound of formula (I): (R)2Al-OR 1 (I) [wherein each R is independently selected from a C1-C3 alkyl group; R 1 is a C1-C3 alkyl group], comprising about 1200 ppm or less of a trimer or tetramer of the compound of formula (I), and / or about 2500 ppm or less of a trimer / tetramer combination of the compound of formula (I).

[0026] In some embodiments, the compound contains about 1200 ppm or less, about 1000 ppm or less, about 900 ppm or less, about 800 ppm or less, or about 700 ppm or less of a trimer or tetramer of the compound of formula (I). In some embodiments, the compound may also contain about 2500 ppm or less, about 2250 ppm or less, about 2000 ppm or less, about 1750 ppm or less, about 1500 ppm or less, or about 1250 ppm or less of a combination of trimers and tetramers of the compound of formula (I).

[0027] In one embodiment of this aspect, the compound of formula (I) is dimethylaluminum isopropoxide.

[0028] In another embodiment, the present disclosure provides a compound represented by formula (II): (R)Al-(OR 1 )2(II) wherein each R is independently selected from a C1 to C8 alkyl group; 1 is a C1-C8 alkyl group. The present invention provides a method for preparing a compound of the formula: The method comprises: (i) a solution comprising a compound of formula (R)Al and a non-coordinating solvent; and (ii) a compound of formula Al(OR 1 ) mixing a solution comprising a compound of formula 3 and a non-coordinating solvent.

[0029] Suitable non-coordinating solvents for the process for preparing compounds of formula II are described above for compounds of formula I. Exemplary compounds of formula (II) include those having R and R 1 is the same as described above for compounds of formula I. According to embodiments of the present invention, the molar stoichiometry can be adjusted to specifically isolate compounds of formula (II).

[0030] In one embodiment, the compound of formula (II) is diethoxyethylaluminum.

[0031] The following examples further illustrate the invention but, of course, should not be construed as in any way limiting its scope. EXAMPLES

[0032] Example 1 Aluminum isopropoxide (445 g, 2.18 mol, 1.05 equiv.) was placed in a 5 L vessel and dissolved in 2.5 kg of heptane to produce a 15 weight percent solution. Trimethylaluminum (300 g, 4.16 mol, 1.00 equiv.) was placed in a 5 L vessel and diluted with 1.2 kg of heptane to produce a 20 weight percent solution. Both vessels were connected to a flow reactor equipped with two needle nose valves, two static mixers, a 3 ft coil, two temperature probes, and a 12 L receiver. Both room temperature solutions were run through the reactor while maintaining the temperature between 20°C and 40°C. An increase in temperature compared to ambient was observed on both temperature probes, indicating that the reaction was occurring. Samples were taken immediately after the end of the flow solutions. 1 H NMR spectroscopy showed complete conversion to dimethylaluminum isopropoxide (crude purity 89%) with no trimethylaluminum remaining. The solvent was removed at 50° C. and the product was distilled under vacuum at 60° C. to give a clear, colorless solution of dimethylaluminum in 75% yield. The trimer content was determined to be 400 ppm and the tetramer content to be 1200 ppm. The results demonstrate that it is possible to obtain a compound of formula (I) having less than about 1200 ppm of trimer or tetramer of the compound of formula (I) and less than about 2500 ppm of the sum of trimers / tetramers of the compound of formula (I).

[0033] Example 2 Aluminum isopropoxide (445 g, 2.18 mol, 1.05 eq) was placed in a 5 L vessel and dissolved in 2.5 kg of heptane to produce a 15 weight percent solution. The aluminum isopropoxide was filtered through a glass frit into another 5 L vessel. Trimethylaluminum (300 g, 4.16 mol, 1.00 eq) was placed in a 5 L vessel and diluted with 1.2 kg of heptane to produce a 20 weight percent solution. Both vessels were connected to a 12 L receiving vessel in a simple flow reactor equipped with two needle nose valves, two static mixers, a 3 ft coil, and two temperature probes. Both room temperature solutions were flowed through the reactor while maintaining the temperature between 20°C and 40°C. An increase in temperature compared to ambient was observed on both temperature probes, indicating that the reaction was occurring. Samples were taken immediately after the end of the flow solutions. 1 H NMR spectroscopy showed complete conversion to dimethylaluminum isopropoxide (crude purity 88 percent) with no trimethylaluminum remaining. The solvent was removed at 50° C. and the product was distilled under vacuum at 60° C. to give a clear, colorless solution of dimethylaluminum in 75% yield. The trimer content was measured to be 170 ppm and the tetramer content was measured to be 490 ppm. The results demonstrate that it is possible to obtain a compound of formula (I) having no more than about 1200 ppm of trimer or tetramer of the compound of formula (I) and no more than about 2500 ppm of the total trimer / tetramer of the compound of formula (I).

[0034] Example 3 Isopropanol (6.1 g, 0.10 mol, 1.02 equiv.) was placed in a 50 mL vessel and diluted with 43 mL of heptane to produce a 15 wt. % solution. Trimethylaluminum (2.0 M, 50 mL, 0.10 mol, 1.00 equiv.) was charged to the 50 mL vessel. Both vessels were connected to a simple flow reactor equipped with a static mixer, a 3 ft coil, and two temperature probes and a 500 mL receiving vessel. Both room temperature solutions were flowed through the reactor while maintaining the temperature between 25°C and 85°C. A higher temperature was observed on the first temperature probe, indicating that the reaction was occurring. A sample was taken immediately after the end of the flow solution.1 H NMR spectroscopy showed 98% conversion to dimethylaluminum isopropoxide (crude purity 95%) with 2% trimethylaluminum remaining.

[0035] Example 4 Trimethylaluminum in heptane (2.0 M, 5 mL, 0.01 mol, 1.00 equiv.) was placed in a 40 mL vial containing a stir bar. A 20 wt. % ethanol solution in heptane (0.46 g, 0.01 mol, 1.0 equiv.) was added slowly to the trimethylaluminum over 5 min with stirring while observing gas evolution. The reaction temperature was maintained between 25°C and 85°C and samples were taken immediately after addition was complete. 1 H NMR spectroscopy showed 85% conversion to dimethylaluminum ethoxide with 5% trimethylaluminum remaining.

[0036] Example 5 Trimethylaluminum in heptane (2.0 M, 5 mL, 0.01 mol, 1.00 equiv.) was placed in a 40 mL vial containing a stir bar. A 20 wt. % solution of methanol in heptane (0.32 g, 0.01 mol, 1.0 equiv.) was added slowly to the trimethylaluminum over 5 min with stirring, observing gas evolution. The reaction temperature was maintained between 25°C and 85°C, and samples were taken immediately after addition was complete. 1 H NMR spectroscopy showed 76% conversion to dimethylaluminum methoxide with 19% trimethylaluminum remaining.

[0037]

[0037] The conversion values ​​were obtained using a 400mHz Burker instrument. 1 The purity profiles described were determined by gas chromatography (Agilent 7890B equipped with a 5977 quadrupole MSD). Separation was achieved on a GC column. At the outlet, the molecules were ionized using electron impact ionization (70 eV). The MSD collected complete mass spectra (10-700 amu) approximately once per second.

[0038] Features of the present invention

[0039] In a first aspect, the present disclosure provides a compound of formula (I): (R)2Al-OR 1 (I) wherein each R is independently selected from a C1 to C8 alkyl group; 1 is a C1-C8 alkyl group. A process for preparing a compound of the formula: The method comprises: (i) a solution comprising a compound of formula (R)Al and a non-coordinating solvent; and (ii) a compound of formula Al(OR 1 ) mixing a compound of formula 3 with a solution comprising a non-coordinating solvent.

[0039]

[0040] In a second aspect, the present disclosure provides a compound of formula (I): (R)2Al-OR 1 (I) wherein each R is independently selected from a C1 to C8 alkyl group; 1 is a C1-C8 alkyl group. A process for preparing a compound of the formula: The method comprises: (i) a solution comprising a compound of formula (R)3Al and a non-coordinating solvent; and (ii) a compound of formula HOR 1 and a solution comprising a non-coordinating solvent.

[0040]

[0041] In a third aspect, the disclosure provides the method of the first or second aspect, wherein R is selected from methyl, ethyl, n-propyl, and isopropyl.

[0041]

[0042] In a fourth aspect, the present disclosure provides a compound comprising: 1 is selected from methyl, ethyl, n-propyl, and isopropyl.

[0042]

[0043] In a fifth aspect, the disclosure provides the method of any one of the first to fourth aspects, wherein the compound of formula (I) is dimethylaluminum isopropoxide.

[0043]

[0044] In a sixth aspect, the present disclosure provides the method of any one of the first to fifth aspects, wherein the mixing is performed in a static mixer.

[0044]

[0045] In a seventh aspect, the present disclosure provides the method of any one of the first to sixth aspects, wherein the non-coordinating solvent is selected from a hydrocarbon having from 5 to 8 carbon atoms.

[0045]

[0046] In an eighth aspect, the present disclosure provides the method of the seventh aspect, wherein the non-coordinating solvent is selected from n-hexane and n-heptane.

[0046]

[0047] In a ninth aspect, the present disclosure provides the method of any one of the first to seventh aspects, wherein the non-coordinating solvent is selected from benzene, toluene, and xylene.

[0047]

[0048] In a tenth aspect, the present disclosure provides the method of any one of the first to ninth aspects, wherein the mixing is carried out at a temperature greater than about 10°C.

[0048]

[0049] In an eleventh aspect, the present disclosure provides the method of any one of the first to ninth aspects, wherein the mixing is carried out at a temperature of about 10°C to about 95°C.

[0049]

[0050] In a twelfth aspect, the present disclosure provides a method of any one of the first to ninth aspects, wherein the mixing is carried out at a temperature of from about 10° to about 40°C.

[0050]

[0051] In a thirteenth aspect, the present disclosure provides the method of any one of the first to twelfth aspects, wherein the mixing is carried out in two or more static mixers connected in series.

[0051]

[0052] In a fourteenth aspect, the present disclosure provides a method of any one of the first to twelfth aspects, wherein the compound of formula (R)3Al is dissolved in the non-coordinating solvent at a concentration of about 0.5 to about 5.0 M.

[0052]

[0053] In a fifteenth aspect, the present disclosure provides a compound of formula Al(OR 1 ) The method of any one of the first or third to fourteenth aspects is provided, wherein the compound of formula (3) is dissolved in a non-coordinating solvent at a concentration of about 0.2 to about 4.0 M.

[0053]

[0054] In a sixteenth aspect, the present disclosure provides a method of any one of the first to fifteenth aspects, further comprising the step of distilling the compound of formula (R)3Al prior to use.

[0054]

[0055] In a seventeenth aspect, the present disclosure provides a compound of formula Al(OR 1 The method according to the first or third to sixteenth aspects further comprises the step of filtering the compound of formula 3.

[0055]

[0056] In an eighteenth aspect, the present disclosure provides a compound represented by formula (I): (R)2Al-OR 1 (I) wherein each R is independently selected from a C1 to C8 alkyl group; 1 is a C1 to C8 alkyl group, and the compound contains about 20 to about 2000 ppm of a non-coordinating solvent.

[0056]

[0057] In a nineteenth aspect, the disclosure provides a compound of the eighteenth aspect, wherein the compound of formula (I) is dimethylaluminum isopropoxide.

[0057]

[0058] In a twentieth aspect, the present disclosure provides a compound represented by formula (I): (R)2Al-OR 1 (I) [wherein each R is independently selected from a C1-C3 alkyl group; R 1 is C1-C3 alkyl], comprising about 1200 ppm or less of a trimer or tetramer of the compound of formula (I), and / or about 2500 ppm or less of a trimer / tetramer combination of the compound of formula (I).

[0058]

[0059] In a twenty-first aspect, the disclosure provides the compound of the twentieth aspect, wherein the compound of formula (I) is dimethylaluminum isopropoxide.

[0059]

[0060] In a twenty-second aspect, the present disclosure provides a compound of formula (I): (R)2Al-OR 1 (I) wherein each R is independently selected from a C1 to C8 alkyl group; 1 is a C1-C8 alkyl group, comprising about 20 to about 2000 ppm of a non-coordinating solvent, the compound being prepared by the method of any one of the first to seventeenth aspects.

[0060]

[0061] In a twenty-third aspect, the present disclosure provides a compound of the twenty-second aspect, which is dimethylaluminum isopropoxide.

[0061]

[0062] In a twenty-fourth aspect, the present disclosure provides a compound represented by formula (I): (R)2Al-OR1 (I) wherein each R is independently selected from a C1 to C8 alkyl group; 1 is a C1-C8 alkyl group, the method comprising: (i) mixing a solution comprising a compound of formula (R)3Al and a non-coordinating solvent with (ii) a compound of formula Al(OR1)3 free of solvent.

[0062]

[0063] Although several exemplary embodiments of the present disclosure have been described above, those skilled in the art will readily appreciate that still other embodiments may be made and used within the scope of the claims appended hereto. Numerous advantages of the disclosure covered in this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, merely illustrative. The scope of the disclosure is, of course, defined in the language in which the appended claims are expressed.

Claims

1. A process for preparing a compound of formula (I), comprising the steps of: (R) ２ Al-OR １ (I) [wherein each R is C １ ~C ８ alkyl groups; R １ is C １ ~C ８ is an alkyl group. (i) Formula (R) ３ (ii) a solution comprising a compound of formula Al(OR １ ) ３ and a solution comprising a non-coordinating solvent.

2. A process for preparing a compound of formula (I), comprising the steps of: (R) ２ Al-OR １ (I) [wherein each R is C １ ~C ８ alkyl groups; R １ is C １ ~C ８ is an alkyl group. (i) Formula (R) ３ (ii) a solution comprising a compound of formula HOR １ and a solution comprising a non-coordinating solvent.

3. 3. The method of claim 1 or 2, wherein R is selected from methyl, ethyl, n-propyl, and isopropyl.

4. R １ The method of any one of claims 1 to 3, wherein is selected from methyl, ethyl, n-propyl, and isopropyl.

5. 5. The process according to any one of claims 1 to 4, wherein the compound of formula (I) is dimethylaluminum isopropoxide.

6. The method of any one of claims 1 to 5, wherein the mixing is carried out in a static mixer.

7. A process according to any one of claims 1 to 6, wherein the non-coordinating solvent is selected from hydrocarbons having from 5 to 8 carbon atoms.

8. The process of claim 7, wherein the non-coordinating solvent is selected from n-hexane, n-heptane and isomers thereof.

9. 7. The method of claim 1, wherein the non-coordinating solvent is selected from benzene, toluene, and xylene.

10. 7. The process according to any one of claims 1 to 6, wherein the non-coordinating solvent is selected from heavy, high-boiling hydrocarbons having from 12 to 18 carbon atoms.

11. The method of claim 10, wherein the non-coordinating solvent is selected from the hydrocarbons n-dodecane, and n-tetradecane, and isomers thereof.

12. 7. The method of any one of claims 1 to 6, wherein the non-coordinating solvent is a mixed high boiling hydrocarbon such as an isoparaffinic fluid.

13. 13. The method of any one of claims 1 to 12, wherein the mixing is carried out at a temperature greater than about 10°C.

14. The method of any one of claims 1 to 13, wherein the mixing is carried out at a temperature of from about 10°C to about 95°C.

15. The method of any one of claims 1 to 14, wherein the mixing is carried out at a temperature of from about 10°C to about 40°C.

16. 16. The method of any one of claims 1 to 15, wherein the mixing is carried out in two or more static mixers connected in series.

17. Formula (R) ３ 17. The method of any one of claims 1 to 16, wherein the compound of Al is dissolved in a non-coordinating solvent at a concentration of about 0.5 to about 5.0 M.

18. Formula Al(OR １ ) ３ The method of any one of claims 1 to 17, wherein the compound of is dissolved in a non-coordinating solvent at a concentration of about 0.2 to about 4.0 M.

19. Before use, ３ 19. The method of claim 1, further comprising the step of distilling the compound of Al.

20. Before use, １ ) ３ 2. The method of claim 1, further comprising the step of filtering the compound.

21. Formula (I): (R) ２ Al-OR １ (I) [wherein each R is C １ ~C ８ alkyl groups; R １ is C １ ~C ８ is an alkyl group. A compound comprising from about 20 to about 2000 ppm of a non-coordinating solvent.

22. 22. The compound of claim 21, wherein the compound of formula (I) is dimethylaluminum isopropoxide.

23. Formula (I): (R) ２ Al-OR １ (I) [wherein each R is C １ ~C ３ alkyl groups; R １ is C １ ~C ３ is an alkyl group. A compound comprising no more than about 1200 ppm of a trimer or tetramer of a compound of formula (I) and / or no more than about 2500 ppm of a trimer / tetramer combination of a compound of formula (I).

24. 24. The compound of claim 23, wherein the compound of formula (I) is dimethylaluminum isopropoxide.

25. A process for preparing a compound of formula (I), comprising the steps of: (R) ２ Al-OR １ (I) [wherein each R is C １ ~C ８ alkyl groups; R １ is C １ ~C ８ is an alkyl group. (i) Formula (R) ３ (ii) a solution comprising a compound of formula Al(OR １ ) ３ and mixing the compound of formula (I).

26. 26. The compound of claim 25, wherein the compound of formula (I) is dimethylaluminum isopropoxide.

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