Azidophosphenium Cations: Versatile Reagents in Inorganic Synthesis

This work describes the synthesis
and characterization of a series
of iminophosphorane-substituted phosphenium cations of the type [R2NPNP­(Cl)2NPNR′2]­[GaCl4] [R = iPr; R′ = iPr (7­[GaCl4]), SiMe3 (8)], which are directly derived from azidophosphenium
salt [iPrNPN3]­[GaCl4] (2iPr­[GaCl4]) and the corresponding chlorophosphane
R2NPCl2. The reactivity of 7­[GaCl4] toward 2,3-dimethylbutadiene
(dmb) and 2,2′-bipyridine (bipy) was investigated, resulting
in the formation of 7-dmb­[GaCl4] and 7-Cl. In addition, self-condensation
of [(Me3Si)2NPN3]­[GaCl4] (2SiMe3[GaCl4]) was studied in detail, and [(Me3Si)2NPNP­(XY)­N­(SiMe3)2]­[GaCl4] [X = Cl; Y = Cl (13), N3 (14)] were determined as products on the basis of 31P NMR spectroscopy. The reaction of 2SiMe3[GaCl4] with [(Me3Si)2NPCl]­[GaCl4] (1SiMe3[GaCl4]) yielded an unprecedented bicyclic 1,3,2λ3,4λ5-diazadiphosphetidine (15), which was formed via a GaCl3-assisted Me3SiCl elimination starting from 13. Furthermore, cations
of the type [R2NPNPR′3]­[GaCl4] [R = iPr; R′ = cHex (19)] were obtained by the effective combination of 2R­[GaCl4] (R = iPr,
SiMe3) with PR′3 (R′ = Ph, cHex). Azidochlorophosphanes R2NP­(N3)Cl [R = iPr, SiMe3 (20R)] are shown to be accessible when 2R­[GaCl4] was combined with bipy. All new compounds
were 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 analysis.