Reactions of [t-Bu2SnO]3 with [t-BuX2Si]2 (X = F, Cl).: Syntheses and structures of novel stannasiloxanes and of [(t-Bu2FSn)2O]2, the first fluorine-containing tetraorganodistannoxane

Di-tert-butyltin oxide, (t-Bu2SnO)(3) (1), reacts with 1,2-di-tert-butyltetrachlorodisilane, (t-BuCl2Si)(2) (2), to provide the stannasiloxane t-Bu2Sn[OSi(OSnCl-t-Bu-2)-t-Bu](2) (4, racemate). The reaction of 1 with 1,2-di-tertbutyltetrafluorodisilane, (t-BuF2Si)(2) (3), provides the stannasiloxane [t-Bu(F)SiOSn-t-Bu-2](2)O (5, meso/racemate mixture) and the tetraorganodistannoxane [t-Bu-2(F)SnOSn(F)-t-Bu-2](2) (6). Under loss of 1/3 mole equiv of 1, the stannasiloxane 5 is transformed into t-Bu2Sn[OSi(F)-t-BuSi(F)-t-BuO](2)Sn-t-Bu-2 (7). Its ten-membered ring structure was elucidated by X-ray analysis. In solution, 7 forms the five-membered ring t-Bu2Sn[OSi(F)-t-Bu](2) (7a). The dimeric nature of 6 was confirmed by its crystal structure determination. In solution, 6 exhibits a unique valence tautomerism as evidenced by F-19 and Sn-119 NMR spectroscopy.