Elektronenreiche Olefine, 3 / Electron Rich Olefins, 3: Bildung des ersten Ν,N′-persilylierten 1,4-Diaminoethens über eine 1,2,3-Triazolin(4)-Zwischenstufe mit 8 cyclisch konjugierten π-Elektronen und 3 benachbarten N-Elektronenpaaren / Formation of the First N,N′-Persilylated 1,4-Diaminoethene via a l,2,3-Triazoline(4)-Intermediate with 8 Cyclically Conjugated π Electrons and 3 Neighbouring Ν Electron Pairs

Exhaustive reductive silylation of 2-trimethylsilyl-1,2,3-triazole (1) using Me,SiCl/K yields the new E-1,1,4,4-tetrakis(trimethylsilyl)-l,4-diazabutene(2) (4) as final product together with N(SiMe 3 ) 3 . Initial reductive 1,4-addition to 1 leads to formation of 1.2.3-tris(trimethylsilyl)-1,2,3-triazoline(4) (2) as an intermediate which is rapidly reduced and silylated further to give the butene 4. Partial π overlap within the five-membered ring 2 containing 8 π electrons and three neighbouring unshared electron pairs is evident from NMR shifts and electron transfer reaction with TCNE. Photoelectron spectroscopy of 4 and the lability of its radical cation 4 +. as studied by ESR show that this system cannot adopt a planar conformation in contrast to the tetrazene(2) analogue.