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)]

✍ Scribed by Scott B. Clendenning; Peter B. Hitchcock; Michael F. Lappert; Philippe G. Merle; John F. Nixon; László Nyulászi

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 244 KB
• Volume: 13
• Category: Article
• ISSN: 0947-6539
• DOI: 10.1002/chem.200601626

✦ Synopsis

Abstract

Treatment of the lithium amide Li[NPh(SiMe~3~)] with 2,4,6‐tri‐tert‐butyl‐1,3,5‐triphosphabenzene, P~3~C~3~__t__Bu~3~, 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, LiP~2~C~3~__t__Bu~3~ (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[3.2.0.0^2,7^]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.