(Di-tertbutylmethylsilyl)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 SiF4 give the mono‐ (2), bis‐ (3), tris‐ (4), and tetrakis‐ (5) ‐[(di‐tert‐butylmethylsilyl)amino]silanes. Lithiated 3 reacts with Me3SiCl 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 19F‐NMR spectrum proves that the Li–F bond fluctuates in solution. Reactions of 1 with (Me3Si)2C(SiF3)2 afford different products (9, 10) by controlling the reaction sequence. An excess of 1 reacts to give a four‐membered CSi2N 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.