Reactions of 1,3,5-triazine with organolithium compounds containing trimethylsilyl substituents; X-ray structures of 1,3,5-triaza- and 1,3,5,7-tetraaza-heptatrienyllithium compounds†

Abstract

While treatment of 1,3,5-triazine NC(H)NC(H)NCH 1 with a [LiCH₂R]₆, b [LiCHR₂]_∞ or c [LiSiR₃(thf)₃] (R = SiMe₃) was believed to yield the 1,4-adducts LiNC(H)NC(H)(R′)NCH 2a–c, by contrast, 1 with [LiNR₂]₃ or [Li(thf)₄][Li(CR₃)₂] under similar conditions gave the 1,3,5,7-tetraazaheptatrienyllithium [Li₃{RNC(H)NC(H)NC(H)NR}₃] 4 or 1,3,5-triazaheptatrienyllithium [Li₂{RNC(H)NC(H)NC(H)CR₂}₂(µ-thf)] 5 compounds, implicating a trimethylsilyl-shift and subsequent ring-scission. For 2b, the transformation to the 1,3,5-triazaheptatrienyllithium compound [Li₄{RNC(H)NC(H)NC(H)C(H)R}₄] 7 was accomplished by heating the solid to 140 °C. Although compound 4 was unreactive towards tmen or pmdien, from the triazaheptatrienyllithium compound 5 and pmdien, the lithium compound [Li{RNC(H)NC(H)NC(H)CR₂}(pmdien)] 6 was isolated. The tri- 4, di- 5, tetra- 7 and mono-nuclear 6 lithium compounds have been fully characterised, including their X-ray crystal structures.