Salts of the first crystallographically characterized chlorophosphinophosphonium ions have been prepared, and their reaction with Ph3P results in reductive coupling of the chlorophosphine centers to give the first acyclic 2,3-diphosphino-1,4-diphosphonium ions, representing a key framework in the development of catena-phosphorus chemistry. These new salts of general formula [R3P-PR'-PR'-PR3][OTf]2 are also obtained in a one-pot diastereoselective reaction of a dichlorophosphine, a tertiary phosphine, and trimethylsilyltrifluoromethanesulfonate. The structural and spectroscopic features of the new dications complement those of the known diphosphonium and 2-phosphino-1,3-diphosphonium dications. Quantitative ligand exchange reactions are observed when derivatives of [Ph3P-PR'-PR'-PPh3][OTf]2 are combined with Me3P, demonstrating the coordinative nature of the phosphine-phosphonium P-P bonds and implicating a bonding model involving the diphosphenium dication acceptor. The observed solid state structures have been interpreted in the context of computational studies.