(Di‐ tert butylmethylsilyl)amide – a Building Block for Azasilacyclobutane Synthesis

Di‐ tert ‐butylmethylsilylamide reacts with n ‐BuLi to give the tetrameric lithium di‐ tert ‐butylmethylsilylamide 1 . Reactions of lithium (di‐ tert ‐butylmethylsilyl)amide 1 with SiF 4 give the mono‐ ( 2 ), bis‐ ( 3 ), tris‐ ( 4 ), and tetrakis‐ ( 5 ) ‐[(di‐ tert ‐butylmethylsilyl)amino]silanes. Lithiated 3 reacts with Me 3 SiCl to form (di‐ tert ‐butylmethylsilyl‐trimethylsilyl)amino‐(di‐ tert ‐butylmethylsilyl)amino‐difluorosilane ( 6 ); the 1,3‐diaza‐2,4‐disilacyclobutane 7 is obtained by LiF elimination. The lithium derivative of 6 (compound 8 ) crystallizes with formation of a (SiFNLi) four‐membered ring system. The 19 F‐NMR spectrum proves that the Li–F bond fluctuates in solution. Reactions of 1 with (Me 3 Si) 2 C(SiF 3 ) 2 afford different products ( 9, 10 ) by controlling the reaction sequence. An excess of 1 reacts to give a four‐membered CSi 2 N ring system, the 1‐(di‐ tert ‐butylmethylsilyl)‐2,4‐bis‐[(di‐ tert ‐butylmethylsilyl)‐amino]‐2,4‐difluoro‐3‐bis(trimethylsilyl)‐1‐aza‐2,4‐disila‐cyclobutane ( 9 ), disubstitution with formation of bis[(di‐ tert ‐butylmethylsilyl)aminodifluorosilyl]bis(trimethylsilyl)methane ( 10 ) occurs in a molar ratio of 2:1. The cyclodisilazane 11 is obtained from dilithiated 10 in an intramolecular interconversion reaction. The crystal structures of 1, 8, 9 , and 11 are reported.