Protic N‑Heterocyclic Germylenes and Stannylenes: Synthesis and Reactivity

The monoalkylated or monoarylated o-phenylenediamines 1a–d (1a, R = t-Bu; 1b, R
= adamantyl; 1c, R = phenyl; 1d, R = mesityl)
react via transamination with Ge­[N­(SiMe3)2]2 or Sn­[N­(SiMe3)2]2 to give
the protic benzimidazolin-2-germylenes 2a–d or the benzimidazolin-2-stannylenes 3a,b. Germylenes 2a,b can be deprotonated
to give the salts Na-4a and Na-4b, each
containing an anionic N-deprotonated N-heterocyclic germylene. The
protic stannylenes 3a,b react with NaH presumably
via reduction of the tin­(II) center by the deprotonated electron-rich o-phenylenediamine ligand and release of elemental tin.
To prevent this reduction, the electron-poor N-H,N′-H-5,6-dibromobenzimidazolin-2-stannylene (5) was prepared and successfully N-deprotonated to give an
anionic stannylene in Na-6. The molecular structures
of 2a, 3a, and Na-4a were established
by X-ray diffraction studies.