Tert-Butylalumoxanes: Synthetic Analogs for Methylalumoxane (MAO) and New Catalytic Routes to Polyolefins and Polyketones
Abstract
The hydrolysis of Al(tBu)3 in toluene using the hydrated salt, A12(SO4)3.14(H20), results in the formation of the dimeric hydroxide (TBu) 2Al(mu-OH)2 (1) and Al4(tBu)7(mu 3-0)2(mu-OH)(2) as the major and minor products, respectively. Compound 1 may also be prepared by the addition of water to a refluxing toluene solution of A1(tBu)3. Compound 1 is remarkably stable to thermolysis and is converted slowly to a mixture of alumoxane species. Dissolution of compound 1 in MeCN or THF yields the hydrogen-bound trimeric complexes (TBu)2A1(mu-OH)3.n(MeCN) n = 1(3), 2 and (TBu)2 Al(mu-OH)3.2(THF), respectively. The large scale synthesis of alumoxanes from the low temperature thermolysis of the trimeric hydroxide. (TBu)2A1(mu-OH)3, allows for the isolation of the penta-aluminum compound Al5(tBu)7(mu-3-0)2(mu-OH)2 (4) and the heptameric alumoxane (TBu)Al(mu 3-O)7 (5). The structure of compound 4 is consistent with the condensation of (TBu)2 Al(mu-OH)3 with (TBu)2Al(mu-OH)2. Thermolysis of 4 yields an alumina gel. The structural relationship of 4 with respect to the structures reported for non-alkyl alumoxanes and alumina gels is discussed. Reaction of (TBu)2Ga(mu-OH)3 with Al(tBu)3 in toluene yields the octameric alumoxane Ga(tBu)3 and (TBu)A1(mu3-0)8 (6), as the major isolable products. Mass spectrometry indicates the incorporation of low levels of gallium (< 8 %) into samples of 6 made by this route. The molecular structures of compounds 2, 4 and 6 have been determined by X-ray crystallograhy.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 16, 1994
- Accession Number
- ADA280532
Entities
People
- Andrew R. Barron
- C. J. Harlan
- Mark R. Mason
Organizations
- Harvard University