PUB - Publikationen an der Universität Bielefeld

Condensation reactions of cyclopentadienyl silanetriols with titanium alkoxides yield oligomeric titanasiloxanes in high yields. Two types of polyhedral structures can be obtained by small structural modifications at the reactants ((CpSi)-Si-R(OH)(3), Ti(OR)(4)) or by variation of reaction parameters. Thus, reaction of the silanetriols 9-(Me3Si)Fluorenyl-Si(OH)3 (1) and CP*Si(OH)(3) (2) with Ti((OBU)-B-t)(4) leads to the cubic Ti4O12Si4 polyhedrons [9-(Me3Si)Fluorenyl-Si](4)O-12[(TiOBu)-Bu-t](4) (3) and [CP*Si](4)O-12[(TiOBU)-B-t](4) (4), respectively, while co-condensations of 1 with Ti((OPr)-Pr-i)(4) afford either the polyhedral titanasiloxane [9-(Me3Si)Fluorenyl-Si](4)O-12[Ti-(OPr)-Pr-i](6)[mu(2)-(PrO)-Pr-i](2)[mu (3)-O](2) (6) or the cubic polyhedron [9-(Me3Si)Fluorenyl-Si](4)O-12[(TiOPr)-Pr-i](4) (5), depending on the choice of temperature and solvent. Substitution reactions with Ph3SiOH, Me2NOH, or acetylacetone at the titanium centers proceed selectively under conservation of the respective TiOSi core structures, whereas substitution reactions at the silicon centers performed with ethanol, HCl, and water are connected with core degradation. Both the novel titanasiloxanes and their titanium-functionalized derivatives have been characterized by IR and NMR spectroscopy as well as by single-crystal X-ray diffraction studies. Thermolysis of 3 leads to quantitative formation of 9-(Me3Si)Fluorene and 2-methylpropene.