Nucleophilic substitution reactions of the tricyclic triphosphorus cage P3(CBut)2: a novel route to polyphosphorus phosphenium complexes

Abstract

Substitution of Cl⁻ in the tricyclic triphosphorus cage Cl(P¹)-P₃(CBu^t)₂ by a range of both anionic and neutral nucleophiles has been investigated. With anionic nucleophiles, reaction with fluoride and hydride anion was shown to afford F(P¹)-P₃(CBu^t) and H(P¹)-P₃(CBu^t)₂ respectively. Subsequent deprotonation of the latter results in the formation of the aromatic anion [1,2,4-P₃(CBu^t)₂]⁻. With neutral nucleophiles, addition of either PMe₃ or PEt₃ to Cl(P¹)-P₃(CBu^t)₂ in the presence of TlOTf results in the formation of the phosphine–phosphenium complexes [(R₃P(P¹)-P₃(CBu^t)₂][OTf] (R = Me or Et): the structure of the methyl-substituted compound was determined by a single crystal X-ray diffraction study. The phosphine ligand in these complexes is extremely labile and addition of I₂ to [(Me₃P(P¹)-P₃(CBu^t)₂]⁺ results in the formation of I(P¹)-P₃(CBu^t)₂.