Structure and bonding of novel acyclic bisaminoarsenium cations.

The synthesis and characterization of a salt bearing a labile bisaminoarsenium cation of the type {[(Me3Si)2N]2As}(+) (9a) are described, which was obtained in the reaction of the chloroarsane [(Me3Si)2N]2AsCl (8) with GaCl3. Reacting 8 with AgOTf did not yield an arsenium salt, but the cyclo-diarsadiazane [(Me3Si)2NAs-μ-NSiMe3]2 (11) was obtained in excellent yields. Moreover, the reactivity of the analogous antimony species [(Me3Si)2N]2SbCl (12) was studied. In the reaction with GaCl3, the aminochlorostibenium salt [(Me3Si)2NSbCl](+)[(Me3Si)2N(GaCl3)2](-) (5) was isolated. In the reaction with AgOTf, substitution of the chlorine in 12 resulted in the formation of [(Me3Si)2N]2SbOTf (13), a compound with significant stibenium character. All new compounds have been fully characterized by means of X-ray, vibrational spectroscopy, CHN analysis, and NMR experiments. All compounds were further investigated by means of density functional theory and the bonding situation was accessed by natural bond orbital (NBO) analysis.