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.