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Synthetic strategies to bicyclic tetraphosphanes using P1, P2 and P4 building blocks
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 31P NMR spectroscopy. All compounds were fully characterized by experimental as well as computational methods.
Reduction of dichloro(diaza-phospha)stibanes – isolation of a donor-stabilized distibenium dication
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.