Formation of cationic [RP5Cl]+-cages via insertion of [RPCl]+-cations into a P-P bond of the P4 tetrahedron

Article abstract of DOI:10.1021/ic2013304

Fluorobenzene solutions of RPCl₂ and a Lewis acid such as ECl₃ (E = Al, Ga) in a 1:1 ratio are used as reactive sources of chlorophosphenium cations [RPCl]⁺, which insert into P-P bonds of dissolved P₄. This general protocol represents a powerful strategy for the synthesis of new cationic chloro-substituted organophosphorus [RP ₅Cl]⁺-cages as illustrated by the isolation of several monocations (21a-g⁺) in good to excellent yields. For singular reaction two possible reaction mechanisms are proposed on the basis of quantum chemical calculations. The intriguing NMR spectra and structures of the obtained cationic [RP₅Cl]⁺-cages are discussed. Furthermore, the reactions of dichlorophosphanes and the Lewis acid GaCl₃ in various stoichiometries are investigated to obtain a deeper understanding of the species involved in these reactions. The formation of intermediates such as RPCl ₂?GaCl₃ (14) adducts, dichlorophosphanylchlorophosphonium cations [RPCl₂-RPCl]⁺ (16⁺) and [RPCl₂-RPCl-GaCl₃]⁺ (17⁺) in reaction mixtures of RPCl₂ and GaCl₃ in fluorobenzene strongly depends on the basicity of the dichlorophosphane RPCl₂ (R = tBu, Cy, iPr, Et, Me, Ph, C₆F₅) and the reaction stoichiometry.