Synthesis of Siloxyalumoxanes and Alumosiloxanes Based on Organosilicon Diols

We have drawn a few interesting conclusions while studying reaction products of Ph(2)Si(OH)(2) with Al((i)Bu)(3) and tetraisobutylalumoxane. In the first place, this is the production (at a Ph(2)Si(OH)(2) and Al((i)Bu)(3) equimolar ratio) of an oligomer siloxyalumoxane structure with alternating four- and six-member rings. In addition, it shows isobutyl and phenyl group migration between aluminum and silicon due to the formation of an intramolecular four-member cyclic complex [Ph(2)(OH)SiO]Al((i)Bu)(2) → [((i)Bu)Ph(OH)SiO]Al((i)Bu)Ph. Ph(2)Si(OH)(2) interaction with Al((i)Bu)(3) not only starts from intramolecular complex production, but the chain is terminated for the same reason, which in the case of the Ph(2)Si(OH)(2) reaction with tetraisobutylalumoxane results in failure of to obtain high-polymer siloxyalumoxane compounds. When Al((i)Bu)(3) interacts with α- and γ-diols, no oligomer compounds are produced. In the Al((i)Bu)(3) reaction with α, γ-diols are created in monomer compounds that are likely to have a cyclic structure. Notably, when Al((i)Bu)(3) interacts with only α-diol, a double excess of Al((i)Bu)(3) allows for full replacement of hydrogen in the α-diol hydroxyl groups by aluminum alkyl residue with 1,3-bis(diisobutylalumoxymethyl)-1,1,3,3-tetramethyldisiloxane production. At an equimolar ratio of initial reagents, the second isobutyl radical at Al does not interact with the second hydroxyl group of α-diol, apparently due to the steric hindrance, and 1-(diisobutylalumoxymethyl)-3-(hydroxymethyl)-1,1,3,3-tetramethyl-disiloxane is produced. Al((i)Bu)(3) reactions with γ-diol also result in monomer compounds, but the presence of a chain consisting of three CH(2)-groups between Si and the hydroxyl group facilitates interaction between the second hydroxyl group of γ-diol and the second isobutyl radical Al((i)Bu)(3). Tetraisobutylalumoxane reactions with α- and γ-diols result in oligomer compounds.