POLYCYCLES AND CAGES IN MOLECULAR ALUMO-POLYSILOXANES—(Ph₂SiO)₈[Al(O)OH]₄ Used as a Supramolecular Target and “Auto-Condensation” Within the Molecule

Abstract

In this preliminary review the reaction of [Ph₂SiO]₈[AlO(OH)]₄ toward 1,3-diaminopropane and hexamethyldisilazane is discussed in view of supramolecular chemistry and access to structural transformations of the original polycycle. Two distinct adducts may be isolated in the first case: [Ph₂SiO]₈[AlO(OH)]₄· 3H₂N-CH₂CH₂CH₂-NH₂ and [Ph₂SiO]₈[AlO(OH)]₄· 2H₂N-CH₂CH₂CH₂-NH₂. Whereas in the 1:3 adduct the four protic hydrogen atoms of the inner Al₄(OH)₄ ring are involved in O…H…N hydrogen bridges to two terminal diaminopropanes and a bridging diaminopropane thus forming an O…H…N(H)₂-CH₂CH₂CH₂N(H)₂ …H…O loop, in the 1:2 adduct two such O…H…N(H)₂-CH₂CH₂CH₂N(H)₂…H…O loops are present. When [Ph₂SiO]₈[AlO(OH)]₄ is allowed to react with hexamethyldisilazane, again two different products may be obtained depending on the solvent: [Ph₂SiO]₈[AlO₂]₂[AlOO-SiMe₃]₂[NH₄· THF]₂ or [Ph₂SiO]₈[AlOO_0.5]₄· 2 py. This last reaction may be viewed as an inner condensation within [Ph₂SiO]₈[AlO(OH)]₄ loosing two equivalents of water. Both products of the reaction with hexamethyldisilazane have an inner Al₂O₂ four-membered cycle in common, to which Al₂O₄Si₂ eight-membered cycles are partly fused.

Keywords:

• Molecular alumosiloxanes
• oxygen connected polycycles with silicon and aluminum
• supramolecular chemistry
• structural chemistry