Silsesquioxane chemistry II. Tin(IV) and hafnium(IV) compounds of silsesquioxanes

Four complexes of silsesquioxanes with di- and triorganotin(IV) cations hav e been prepared; their composition was determined by standard analytical an d spectroscopic methods. The results show that complexes containing an orga notin(IV) moiety and the ligand in a 1:1 ratio are formed. FTIR spectra are consistent with the presence of Sn-O vibrations in the compounds. The stru cture of the complexes is discussed on the basis of Mossbauer and multinucl ear (H-1, C-13, Sn-119, and Si-29) NMR spectroscopic measurements. Comparis on of the experimental quadrupole splitting (QS) with that calculated on th e basis of the partial quadrupole splitting (PQS) concept revealed that the complexes formed with dialkyltin(IV) cations as well as the trialkyl deriv atives have a regular tetrahedral structure. A new organohafnium silsesquio xane derivative ([Cy7Si7O12Hf(C5Me5)], Cy=cyclohexyl, 5), was prepared by t reatment of [Cy7Si7O9(OH)(3)] with (C5Me5)HfMe3 under elimination of methan e. The molecular structure of 5 was determined by X-ray crystallography.