Acyclic catena-Diphosphinodiphosphonium Dications [R₃P-PR‘-PR‘-PR₃]²⁺ or Bisphosphine−Diphosphenium Complexes [R₃P→PR‘-PR‘←PR₃]²⁺:  Synthesis by Reductive P−P Coupling of [R₃P-PR‘Cl]⁺ and Phosphine Ligand Exchange

The acyclic tetraphosphorus dication [Ph₃P-PPh-PPh-PPh₃]²⁺ has been formed by the reductive coupling of [Ph₃P-PPhCl]⁺, providing a new synthetic method for the systematic development of catena-phosphorus cations. Ligand exchange (Ph₃P for Me₃P) gives [Me₃P-PPh-PPh-PMe₃]²⁺, implicating these dications as bisphosphine−diphosphenium complexes.