Synthesis of the 2,4,5‐Tri‐tert‐butyl‐1,3‐diphospholide Anion by Phosphinidene Elimination from 2,4,6‐Tri‐tert‐butyl‐1,3,5‐triphosphabenzene on Treatment with the Amide Li[NPh(SiMe3)]

Treatment of the lithium amide Li[NPh(SiMe3)] with 2,4,6‐tri‐tert‐butyl‐1,3,5‐triphosphabenzene, P3C3tBu3, in a 1:2 ratio afforded equimolar amounts of the lithium salt of the five‐membered 2,4,5‐tri‐tert‐butyl‐1,3‐diphospholide anion, LiP2C3tBu3(isolated as its N,N,N′,N′‐tetramethylethylenediamine (TMEDA) adduct), and the tricyclic compound 6‐[phenyl(trimethylsilyl)amino]‐3,5,7‐tri‐tert‐butyl‐1,2,4,6‐tetraphosphatricyclo[3.2.0.02,7]hept‐3‐ene. Both compounds have been structurally characterised by single‐crystal X‐ray diffraction studies. The mechanism of this remarkable reaction has been elucidated by theoretical methods at the B3LYP/6‐311+G** level of theory. The reaction involves a hitherto unobserved aminophosphinidene, which was formed by abstraction of a phosphorus atom from triphosphabenzene. The intermediate aminophosphinidene, which is further stabilised by the solvent THF, shows, in agreement with previous theoretical predictions, enhanced stability and reacts then with a second molecule of triphosphabenzene.