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

Abstract

[LCRP((PhP)2C2H4)][OTf] (4 a,b[OTf]) and [LCiPrP(PPh2)2][OTf] (5 b[OTf]) were prepared from the reaction of imidazoliumyl-substituted dipyrazolylphosphane triflate salts [LCRP(pyr)2][OTf] (3 a,b[OTf]; a: R=Me, b=iPr; LCR=1,3-dialkyl-4,5-dimethylimidazol-2-yl; pyr=3,5-dimethylpyrazol-1-yl) with the secondary phosphanes PhP(H)C2H4P(H)Ph) and Ph2PH. A stepwise double P−N/P−P bond metathesis to catena-tetraphosphane-2,3-diium triflate salt [(Ph2P)2(LCMeP)2][OTf]2 (7 a[OTf]2) is observed when reacting 3 a[OTf] with diphosphane P2Ph4. The coordination ability of 5 b[OTf] was probed with selected coinage metal salts [Cu(CH3CN)4]OTf, AgOTf and AuCl(tht) (tht=tetrahydrothiophene). For AuCl(tht), the helical complex [{(Ph2PPLCiPr)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(CH3CN)3][OTf]2 (M=Cu, Ag) (10[OTf]2, 11[OTf]2).