SYNTHESIS OF AMINO-FUNCTIONALIZED CYCLOTR ISILOXANES BY SALT-ELIMINATION REACTIONS

The synthesis of amino functionalized cyclotrisiloxanes 4a and 4b can be achieved by novel routes. Controlled hydrolysis of the dichloroamin osilanes 1a, 1b in the presence of triethylamine leads to the novel bi s(amino)chlorosilanols 2a, 2b. They are colourless solids which sublim e without decomposition despite the fact that they combine a Cl and OH function at the silicon atom. In the crystalline phase the compounds form tetramers by oxygen hydrogen bridges as found from X-ray diffract ion on single crystals of 2b. On treatment of 2a and 2b with BuLi the lithium salts 3a and 3b are formed, which crystallize as tetramers in a cubane like oxygen/lithium cage, in which the lithium atoms are coor dinated by three oxygen and one chlorine atom (X-ray structure analysi s on 3a (Li-O 1.923(6) 1.993(6)Angstrom, Li-Cl 2.626(6)Angstrom). The lithium compounds 3a and 3b show an exceptional thermal stability. The y can be recrystallized in hot non-polar solvents without elimination of LiCl. Boiling 3a and 3b in THF for 50 hours nevertheless leads to t he elimination of LiCl and the formation of the amino functionalized c yclotrisiloxanes 4a and 4b as colourless, sublimable compounds. These compounds have been characterized by single X-ray diffraction techniqu es: they have a planar Si3O3 ring in common with three spirocyclic sil icon atoms.