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

Substitution of Cl(-) in the tricyclic triphosphorus cage Cl(P(1))-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(P(1))-P3(CBu(t)) and H(P(1))-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(P(1))-P3(CBu(t))2 in the presence of TlOTf results in the formation of the phosphine-phosphenium complexes [(R3P(P(1))-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(P(1))-P3(CBu(t))2]+ results in the formation of I(P(1))-P3(CBu(t))2.