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

Four complexes of silsesquioxanes with di- and triorganotin(IV) cations have been prepared; their composition was determined by standard analytical and spectroscopic methods. The results show that complexes containing an organotin(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 structure of the complexes is discussed on the basis of Mossbauer and multinuclear ((1)H, (13)C, (119)Sn, and (29)Si) NMR spectroscopic measurements. Comparison of the experimental quadrupole splitting (QS) with that calculated on the basis of the partial quadrupole splitting (PQS) concept revealed that the complexes formed with dialkyltin(IV) cations as well as the trialkyl derivatives have a regular tetrahedral structure. A new organohafnium silsesquioxane derivative ([Cy(7)Si(7)O(12)Hf(C(5)Me(5))], Cy=cyclohexyl, 5), was prepared by treatment of [Cy(7)Si(7)O(9)(OH)(3)] with (C(5)Me(5))HfMe(3) under elimination of methane. The molecular structure of 5 was determined by X-ray crystallography.