Different reactions of Mes* substituted phosphanes (Mes* = 2,4,6-tri-tert-butylphenyl) led to the formation of the bicyclic tetraphosphane Mes*P4Mes* (5) and its unknown Lewis acid adduct 5·GaCl3. In this context, the endo-exo isomer of 5 was fully characterized for the first time. The synthesis was achieved by reactions involving "self-assembly" of the P4 scaffold from P1 building blocks (i.e. primary phosphanes) or by reactions starting from P2 or P4 scaffolds (i.e. a diphosphene or cyclic tetraphosphane). Furthermore, interconversion between the exo-exo and endo-exo isomer were studied by (31)P NMR spectroscopy. All compounds were fully characterized by experimental as well as computational methods.
A reaction of antimonytrichloride SbCl3 with potassium bis(terphenylimino)phosphide K[(TerN)2P] smoothly afforded a novel class of mixed diazadipnictanes, namely dichloro(diaza-phospha)stibane [Ter2N2P((III))Sb((III))Cl2], which is considered to exist as open chain-like and cyclic isomers in an equilibrium. [Ter2N2PSbCl2] is a versatile starting material for reduction and halide abstraction experiments. Halide abstraction led to the formation of a cyclic diazastibaphosphenium cation [P(μ-NTer)2SbCl](+). Upon reduction of [Ter2N2PSbCl2], the transient existence of the novel mixed biradicaloid [P(μ-NTer)2Sb] was proven by a trapping experiment with an alkyne, while reduction in the absence of trapping agents afforded the eight-membered heterocycle [Sb2-{μ-(TerN)2P}2]. This constitutional isomer of a dimerized biradicaloid features a bonding situation that indicates the presence of a donor-stabilized [Sb2](2+) ion.
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.
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