SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF A TETRAARYLDIPHOSPHORUS CATION AND A DIALKYLPHOSPHONIUM SALT

Abstract

The compound 5-chorodibenzophosphole reacts with an equivalent amount or an excess of AI₂CI₆ in methylene chloride solution to afford the respective tetraorganodiphosphorus cations [R₂P(CI)PR₂][AICI₄] (R₂ = o,o'-dibenzophenylato), 1. However, reaction of t -Bu₂PCI with an equivalent amount or an excess of AI₂CI₆ in CH₂CI₂ gives rise to a phosphonium ion, [t -Bu₂PCI₂][AICI₄) (2) as the major product, while reaction with 0.5 equivalent A1₂CI₂ leads to a mixture of cationic organophosphorus species. In addition, the compound 5-chloro-bis-carboranylphosphole (3) was synthesized. Compound 3 fails to react with A1₂C1₂ or GaCl₂, yet does afford 5-fluoro-bis-carboranylphosphole (4) upon treatment with AgSbF₂. The molecular structures of 1 and 2 have been determined from X-ray structural analysis. The former consists of a planar P(HI) heterocyclic moiety joined to an essentially tetrahedral P(1V) heterocycle by a single P[sbnd]P bond. The charge is balanced by the heptachlorodialuminate ion. Compound 1 crystallized in the triclinic space group PI with a = 10.5798(8) Å, b = 11.3656(9) Å, c = 13.8190(11) Å, α = 107.985(3)°, R = 100.9135(2)°, y = 103.636(2)°, γ = 1478 ų, Z = 2, R = 0.047. Compound 2 crystallized in the monoclinic space group, P2₁ with a = 7.2471(8) Å, b = 12.0235(12) Å, c = 9.9651(11) Å, β = 90.473(3)°, V = 868 ų, Z = 2, R = 0.109.

Key Words:

• Synthesis
• X-ray structures
• diphosphorus cation
• phosphonium cation
• heptachloroaluminate ion
• NMR.