The synthesis, crystal structures and NMR spectroscopic investigation of 3,7,10-trimethylsilatranes and carbasilatranes

The first representatives of aryloxy-trimethylsilatranes, C6H5OSi[OCH(CH3)CH2]3N, of aryloxy-carbasilatranes, C6H5OSi(CH2CH2CH2)(OCH2CH2)2N, and a number of novel 3,7,10-trimethylsilatranes (RSi[OCH(CH3)CH2]3N) and carbasilatranes (RSi(CH2CH2CH2)(OCH2CH2)2N) have been prepared and characterised, both structurally and by NMR spectroscopy. The influence of various Si substituents (R = alkyl, aryl, alkoxy and aryloxy) as well as the influence of the substitution in the skeleton of the trimethylsilatranes and carbasilatranes on the chemical shift in the 29Si, 1H and 13C NMR spectra has been investigated. The crystal structures of both diastereomers of phenyl-3,7,10-trimethylsilatrane and of the symmetrical isomer of p-tolyl-3,7,10-trimethylsilatrane were determined by X-ray diffraction after separation of the diastereomers by means of HPLC. All three crystal structures are centrosymmetric.