Reactions of group 14 and group 4 organometallics with polyhedral oligosilsesquioxanes and a comparison with silica

The chemistry of silsesquioxanes and metallasilsesquioxanes can provide important insights into the chemistry of silica and silica supported transition metal catalysts.The polyhedral oligosilsesquioxane [Cy7Si7O9(OH)3], trisilanol, has been modified by base assisted metathesis using a variety of group 14 organometallics, SiMe3Cl, SnMe3Cl and GeMe3Cl. The silicon and tin analogues afford [Cy7Si7O9(OH)2(OEMe3)], where E = Si or Sn. The germanium analogue, however, affords a trisubstituted product [Cy7Si7O9(OGeMe3)3]. The reactions of SiMe2Cl2, SnMe2Cl2 and GeMe2Cl2 with trisilanol yield a mixture of inseparable products, however, if [Cy7Si7O9(OH)2(OTMS)] is reacted with the dimethyl complexes, colourless crystals of [Cy7Si7O11(OTMS)(EMe2)], where E = Si, Sn or Ge, are formed. All these compounds have been primarily characterised by 1H, 13C and 29Si solution NMR spectroscopy as well as solid state 13C and 29Si NMR. Mass spectrometry, infra red spectroscopy, micro analysis and where possible single crystal X-ray diffraction studies have also been performed.The trimethylsilane substituted cage was reacted with group 4 cyclopentadienyl complexes. The reaction with titanium was inconsistent and appeared to produce a mixture of products that were inseparable and never fully characterised. The reactions of Cl2ZrCp2 and Cl2HfCp2 with [Cy7Si7O9(OH)2(OTMS)] yielded only one major product, [Cy7Si7O11(OTMS)(MCp2)], where M = Zr or Hf. The reactions were then performed using the bis(pentamethyl)cyclopentadienyl metal dichloride. The reactions gave a mixture of products in extremely low yields. The metallocenes were modified until a better yield was obtained. It was found that the dimethyl substituted metallocene, Me2MCp*2 (where M = Zr or Hf), gave the cleanest reaction, yielding crystals of [Cy7Si7O11(OTMS)(MCp*2)]. These compounds were again characterised by a variety of techniques, most importantly 1H, 13C and 29Si solution NMR spectroscopy and single crystal X-ray diffraction.