Reduction of dichloro(diaza-phospha)stibanes - isolation of a donor-stabilized distibenium dication

摘要

A reaction of antimonytrichloride SbCl3 with potassium bis(terphenylimino)phosphide K[(TerN)(2)P] smoothly afforded a novel class of mixed diazadipnictanes, namely dichloro(diaza-phospha)stibane [Ter(2)N(2)P((III))Sb((III))Cl(2)], which is considered to exist as open chain-like and cyclic isomers in an equilibrium. [Ter(2)N(2)PSbCl(2)] is a versatile starting material for reduction and halide abstraction experiments. Halide abstraction led to the formation of a cyclic diazastibaphosphenium cation [P(mu-NTer)(2)SbCl](+). Upon reduction of [Ter(2)N(2)PSbCl(2)], the transient existence of the novel mixed biradicaloid [P(mu-NTer)(2)Sb] was proven by a trapping experiment with an alkyne, while reduction in the absence of trapping agents afforded the eight-membered heterocycle [Sb-2-{mu-(TerN)(2)P}(2)]. This constitutional isomer of a dimerized biradicaloid features a bonding situation that indicates the presence of a donor-stabilized [Sb-2](2+) ion.