Tetrafluorcyclodi- und Hexafluorcyclotrisilazane / Tetrafluorocyclodi- and Hexafluorocyclotrisilazanes

Abstract

Bis(silylamino)difluorosilanes (1,2) are prepared in the reaction of lithiated di-tert-butylmethyl- and tert-butyl-dimethylsilylamine with tetrafluorosilane. The dilithium derivative of 1 reacts with SiF4 to give the tetrafluoro-substituted four-membered (Si-N) ring system [(CMe3)2MeSiN-SiF2]2 (3). Two four-membered rings [(RN-SiF2)2 (4), (RN-SiFNRSiF3)2 (5), R=CMe3SiMe2] are obtained in the reaction of dilithiated 2 with SiF4. The dilithiated silylamines and SiF4 also react with formation of 3 and 4. However, besides 4 the six-membered ring (CMe3SiMe2N-SiF2)3(6) is obtained. Crystal structures of 3,5, and 6 were determined. A transannular Si ··· Si ring distance of 237,5 pm is found in 3.