Bis(Trimethylsilyl)Ammonium Salts Obtained by Reaction of Hexamethyldisilazane with TiCl₄, ZrCl₄, or SnCl₄

Abstract

Abstract The reaction of hexamethyldisilazane with TiCl 4 in CH 2 Cl 2 leads to the formation of [(Me 3 SiNTiCl 2 ) 8 ] ( 3 ). According to the crystal structure analysis, 3 is an octameric titanium trimethylsilylimido chloride. The mechanism of the formation of 3 was studied in detail by means of time‐dependent 14 N NMR spectroscopy. [(Me 3 Si) 2 NTiCl 3 ] was identified as an intermediate during the formation of 3 . Two by‐products were identified: [(NH 4 ) 2 TiCl 6 ] and the hitherto unknown bis(trimethylsilyl)ammonium salt [(Me 3 Si) 2 NH 2 ] + [Ti 2 Cl 9 ] − ( 5 ). According to the crystal structure analysis, protonation of hexamethyldisilazane to give the cation of 5 causes a significant lengthening of the Si‐N bond from 173.5 to 186 pm. Other tetravalent metal chlorides, such as ZrCl 4 and SnCl 4 , also reacted with hexamethyldisilazane to yield bis(trimethylsilyl)ammonium salts. However, the constitution of the corresponding anions differs significantly. In the case of ZrCl 4 , an anionic chlorotrimethylsilylimidozirconate ( 6 ) [(Me 3 Si) 2 NH 2 ] + 2 ‐[{Cl 3 ZrCl 3 Zr(Cl)(NSiMe 3 )} 2 ] 2− was obtained, while SnCl 4 reacted to give a novel spiro anion [N(SnCl 3 ) 2 (SnCl 2 ) 4 ‐(NSiMe 3 ) 2 NH) 2 ] − together with the bis(trimethylsilyl)ammonium ion in 7 ; this anion is the first species containing a tetrastannylated nitrogen.