Benzannulated N-heterocyclic germylenes and stannylenes with sterically demanding N,N'-substituents.

Four N,N'-disubstituted 1,2-diaminobenzes (1a: R = t-Bu, 1b: R = adamantyl, 1c: R = Ph, 1d: R = Dipp) have been prepared and reacted with E[N(SiMe3)2]2 (E = Ge, Sn) to give the benzannulated N-heterocyclic germylenes 2a-d and stannylenes 3a-d. Germylene 2d and stannylenes 3a, 3c and 3d have been characterized by X-ray diffraction showing different types of intermolecular interactions in the solid state. Deprotonation of 1b with n-BuLi yields the lithium stannyl anion Li[4] with an n-Bu group bound to the tin(II) center.