Organometallic bases are becoming increasingly complex, because mixing components can lead to bases superior to single-component bases. To better understand this superiority, it is useful to study metalated intermediate structures prior to quenching. This study is on 1-phenyl-1H-benzotriazole, which was previously deprotonated by an in situ ZnCl2• TMEDA/LiTMP (TMEDA=N,N,N′,N′-tetramethylethylenediamine; TMP=2,2,6,6-tetramethylpiperidide) mixture and then iodinated. Herein, reaction with LiTMP exposes the deficiency of the single-component base as the crystalline product obtained was [{4-R-1-(2-lithiophenyl)-1H-benzotriazole• 3THF}2], [R=2-C6H4(Ph)NLi], in which ring opening of benzotriazole and N2 extrusion had occurred. Supporting lithiation by adding iBu2Al(TMP) induces trans-metal trapping, in which C-Li bonds transform into C-Al bonds to stabilise the metalated intermediate. X-ray diffraction studies revealed homodimeric [(4-R′-1-phenyl-1H-benzotriazole)2], [R′=(iBu)2Al(μ-TMP)Li], and its heterodimeric isomer [(4-R′-1-phenyl-1H-benzotriazole){2-R′-1-phenyl-1H-benzotriazole}], whose structure and slow conformational dynamics were probed by solution NMR spectroscopy
