Synthesis of Novel Titanasiloxanes with Ring and Cage Structures Using Sterically Demanding Substituents

Novel oligomeric titanasiloxanes have been synthesized in good yields by reaction of sterically demanding organosilanetriols with titanium alkoxides. The silanetriols t Bu 2 (Me 3 Si)FlSi(OH) 3 ( 5 ), (Me 3 Si)FlSi(OH) 3 ( 6 ), and MeFlSi(OH) 3 ( 7 ) and the titanium alkoxides Ti(OEt) 4, Ti(O i Pr) 4, and Ti(O i Pr) 2 (acac) 2 have been used as starting materials (Fl = fluorenyl). Quite different structures are obtained by only small modifications of the organic substituents of the substrates. Thus, the condensation reactions result in the formation of the polyhedral titanasiloxanes [ t Bu 2 (Me 3 Si)FlSi] 4 O 12 [TiOEt] 4 ( 8 ), [(Me 3 Si)FlSi] 2 O 5 [Ti(OEt)] 4 [μ 2 -OEt] 6 [μ 4 -O] ( 9 ), ([ t Bu 2 (Me 3 Si)FlSi] 3 O 10 [Ti(O i Pr)] 4 [μ 2 -O i Pr] 2 [μ 3 -O]Ti) 2 O ( 10 ), and [MeFlSi] 2 O 8 [Ti(O i Pr)] 6 [μ 2 -O i Pr] 4 [μ 3 -O] 2 [PhNH 2 ] 2 ( 11 ) and the cyclic titanasiloxane [MeFlSi(O i Pr)] 2 O 4 [Ti(acac) 2 ] 2 ( 12 ). A 1:1 stoichiometry of the starting materials leads to 8 and 12 in quantitative yield, while 9 − 11 are isolated in minor quantities. If the appropriate substrate ratio is used, the latter compounds can also be obtained in high yields. All titanasiloxanes have been characterized by X-ray crystallography, NMR, IR, and elemental analysis.