Benzimidazolin-2-stannylenes with N,N'-alkyl (Me and Et) and Lewis base functional groups

Symmetrically and unsymmetrically N,N'-substituted benzimidazolin-2-stannylenes with sterically nondemanding alkyl (Me and Et) and Lewis base functional groups (-(CH2)nOMe, -(CH2)nNMe2; n=2, 3) have been synthesized by the transamination reaction between suitably substituted o-phenylenediamines and SnN(SiMe3)2]2. The N,N'-dimethyl-substituted stannylene 3 exists in the solid state as a bimolecular aggregate which is held together by strong intermolecular Sn...N interactions leading to three-coordinated tin atoms. The benzimidazolin-2-stannylenes with N,N'-(CH2)nOMe substituents (5, n=2; 6, n=3) exhibit weak intramolecular Sn...O interactions in solution. Benzannulated stannylenes with N,N'-(CH2)nNMe2 substituents (7, n=2; 8, n=3) are again dimers which exhibit both intramolecular Sn...NMe2 and intermolecular Sn...N interactions, which leads to tri- or tetracoordinated tin atoms. Some unsymmetrically N,N'-substituted benzimidazolin-2-stannylenes have also been synthesized. The molecular structures of 3, 5, and 8 and the relation between the chemical shift recorded for the tin atoms and the solvent (C6D6 or THF-d8) used for recording 119Sn NMR spectra will be discussed.