Acyclic <i>c</i><i>atena</i>-Diphosphinodiphosphonium Dications [R<sub>3</sub>P-PR‘-PR‘-PR<sub>3</sub>]<sup>2+</sup> or Bisphosphine−Diphosphenium Complexes [R<sub>3</sub>P→PR‘-PR‘←PR<sub>3</sub>]<sup>2+</sup>:  Synthesis by Reductive P−P Coupling of [R<sub>3</sub>P-PR‘Cl]<sup>+</sup> and Phosphine Ligand Exchange

The acyclic tetraphosphorus dication [Ph<sub>3</sub>P-PPh-PPh-PPh<sub>3</sub>]<sup>2+</sup> has been formed by the reductive coupling of [Ph<sub>3</sub>P-PPhCl]<sup>+</sup>, providing a new synthetic method for the systematic development of <i>catena</i>-phosphorus cations. Ligand exchange (Ph<sub>3</sub>P for Me<sub>3</sub>P) gives [Me<sub>3</sub>P-PPh-PPh-PMe<sub>3</sub>]<sup>2+</sup>, implicating these dications as bisphosphine−diphosphenium complexes.