Diaminocarbene homologues: synthesis and crystal structure of the first diaminogermylene LiCl adduct displaying an electrophilic germanium centre

Abstract

2-Chloro-3-tert-butylaminoquinoxaline 1, prepared from 2,3-dichloroquinoxaline and tert-butylamine under elevated temperatures and pressure, reacts with two equivalents of BuLi and a semimolar amount of GeCl₂(dioxane) to form a novel cyclic diamino germylene–LiCl adduct 2 solvated in the crystals by dioxane and two molecules of toluene. The bonding of the chloride ion at germanium of the twofold quinoxaline anellated eight-membered N–Ge–N heterocycle, shown by X-ray crystal structure analysis of 2, indicates electrophilic character and thus umpolung of the usually nucleophilic diaminogermylene structural unit by the electron withdrawing anellation and the ambidentate nature of carbenes. The coordination of each quinoxaline ring system by one of its nitrogen atoms to the lithium cation, fixed in a polymer Li⁺–dioxane backbone, amplifies the electron withdrawing effect.