BIS(TRIMETHYLSILYL)AMMONIUM SALTS OBTAINED BY REACTION OF HEXAMETHYLDISILAZANE WITH TICL4, ZRCL4, OR SNCL4

The reaction of hexamethyldisilazane with TiCl4 in CH2Cl2 leads to the formation of [(Me3SiNTiCl2)(8)] (3). According to the crystal structu re analysis, 3 is an octameric titanium trimethylsilylimido chloride. The mechanism of the formation of 3 was studied in detail by means of time-dependent N-14 NMR spectroscopy. [(Me3Si)(2)NTiCl3] was identifie d as an intermediate during the formation of 3. Two by-products were i dentified: [(NH4)(2)TiCl6] and the hitherto unknown bis(trimethylsilyl )ammonium salt [(Me3Si)(2)NH2](+)[Ti2Cl9](-) (5). According to the cry stal structure analysis, protonation of hexamethyldisilazane to give t he cation of 5 causes a significant lengthening of the Si-N bond from 173.5 to 186 pm. Other tetravalent metal chlorides, such as ZrCl4 and SnCl4, also reacted with hexamethyldisilazane to yield bis(trimethylsi lyl)ammonium salts. However, the constitution of the corresponding ani ons differs significantly. In the case of ZrCl4, an anionic chlorotrim ethylsilylimidozirconate (6) [(Me3Si)(2)NH2](2+) [{Cl3ZrCl3Zr(Cl)(NSiM e3)}(2)](2-) was obtained, while SnCl4 reacted to give a novel spiro a nion [N(SnCl3)(2)(SnCl2)(4)-(NSiMe3)(2)(NH)(2)](-) together with the b is(trimethylsilyl)ammonium ion in 7; this anion is the first species c ontaining a tetrastannylated nitrogen.