P-P Condensation and P-N/P-P Bond Metathesis: Facile Synthesis of Cationic Tri- and Tetraphosphanes

[L_C ^R P((PhP)₂ C₂ H₄ )][OTf] (4 a,b[OTf]) and [L_C ^iPr P(PPh₂ )₂ ][OTf] (5 b[OTf]) were prepared from the reaction of imidazoliumyl-substituted dipyrazolylphosphane triflate salts [L_C ^R P(pyr)₂ ][OTf] (3 a,b[OTf]; a: R=Me, b=iPr; L_C ^R =1,3-dialkyl-4,5-dimethylimidazol-2-yl; pyr=3,5-dimethylpyrazol-1-yl) with the secondary phosphanes PhP(H)C₂ H₄ P(H)Ph) and Ph₂ PH. A stepwise double P-N/P-P bond metathesis to catena-tetraphosphane-2,3-diium triflate salt [(Ph₂ P)₂ (L_C ^Me P)₂ ][OTf]₂ (7 a[OTf]₂ ) is observed when reacting 3 a[OTf] with diphosphane P₂ Ph₄ . The coordination ability of 5 b[OTf] was probed with selected coinage metal salts [Cu(CH₃ CN)₄ ]OTf, AgOTf and AuCl(tht) (tht=tetrahydrothiophene). For AuCl(tht), the helical complex [{(Ph₂ PPL_C ^iPr )Au}₄ ][OTf]₄ (9[OTf]₄ ) was unexpectedly formed as a result of a chloride-induced P-P bond cleavage. The weakly coordinating triflate anion enables the formation of the expected copper(I) and silver(I) complexes [(5 b)M(CH₃ CN)₃ ][OTf]₂ (M=Cu, Ag) (10[OTf]₂ , 11[OTf]₂ ).