Dimerisation of a silicenium ylid by methanide and silylamine migration

The thermal elimination of LiF from lithium aminofluorosilanes provides a simple synthetic route to four-membered silicon-nitrogen rings. In attempts to inhibit sterically the otherwise ready dimerisation of such lithium salts, t-butyl, mesityl and silylamine substituents were introduced. The lithiation of the fluorotris(silylamino)silane (Me3SiNMe)2SiF-NHSiMe2CMe3 and the thermal elimination of LiF led to the formation of a cyclodisilazane, involving migration of a methanide and a silylmethylamine in one of the monomer precursors. The crystal structure of this product has been determined from 3375 unique diffractometer-measured intensities, and refined to R = 0.070. The space group is P21/n, with a 12.458(2), b 22.589(3), c 16.376(4) Å, β 102.33(1)° and Z = 4.