The synthesis and structure of lithium and silver tetrakis(pentafluorophenyl)borate salts have been studied in different solvents ranging from polar (CH 2 Cl 2 , diethyl ether) to nonpolar (toluene, pentane). While Li[B(C 6 F 5 ) 4 ] is stable in all studied solvents and crystallizes with four ether molecules from ether and with two toluene molecules from toluene, the silver salt is only stable when the Ag þ ion is strongly coordinated such as in [Ag(tolueneIn weakly coordinating solvents such as CH 2 Cl 2 Ag[B(C 6 F 5 ) 4 ] decomposes, yielding AgC 6 F 5 and B(C 6 F 5 ) 3 . The overall process of the AgC 6 F 5 synthesis starting from B(C 6 F 5 ) 3 and LiC 6 F 5 can formally be regarded as a B(C 6 F 5 ) 3 -catalyzed reaction. The salt [Ag(toluene) 3 ][B(C 6 F 5 ) 4 ] presents an easily accessible, ether-free, stable silver salt of the [B(C 6 F 5 ) 4 ]anion. All compounds have been fully characterized. § Dedicated to Prof. Dr. Uwe Rosenthal on the occasion of his 60th birthday.

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The reaction of AgC(6)F(5) with monomeric iminophosphanes of Mes*-N═P-X (X = Cl, I) in CH(2)Cl(2) at ambient temperature gives imino(pentafluorophenyl)phosphane, Mes*N═P(C(6)F(5)) (1), in almost quantitative yield (96%), which could be isolated as a highly viscous blue oil. The same reaction with LiC(6)F(5) results in the formation of imino(amino)phosphane (C(6)F(5))(2)P-N(Mes*)-P═NMes* (2) (yield 93%). In the second series of experiments the analogous reaction of MC(6)F(5) (M = Ag, Li) with dimeric [Cl-P(μ-N-Dipp)](2) was studied, leading to the formation of [R-P(μ-N-Dipp)](2) (R = C(6)F(5)) (3) for M = Ag, while only decomposition products such as P(C(6)F(5))(3) were observed in the reaction with the Li salt. Highly labile Mes*-N═P-C(6)F(5) (1) decomposes at ambient temperatures, forming among other products the diphosphane (C(6)F(5))(2)P-P(C(6)F(5))(2) (4). Reaction of 1 with Fe(2)(CO)(9) yields the iron carbonyl complexes Mes*-N═P(C(6)F(5))·Fe(CO)(4) (5) and [Mes*-N═P(C(6)F(5))](2)·Fe(CO)(3) (6). The structure, bonding, and potential energy surface are discussed on the basis of B3LYP/6-31G(d,p) computations. According to time-dependent B3LYP calculations, the blue color of 1 arises from an n → π* electronic transition.

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