Reactions of [SiF4(NH3)2] with Fluorides AF (A = Li-Cs, Tl, NH4) in Liquid NH3: A [NH4(NH3)2]+ Cation and a Thallophilic Interaction in [Tl2(NH3)6]2+

We investigated whether [SiF4(NH3)(2)] can act as a fluoride-ion acceptor in its reactions with the fluorides AF (A = Li-Cs, Tl, NH4) in anhydrous liquid ammonia (NH3). While LiF and NaF did not react, we obtained the compounds K[SiF5(NH3)], Rb[SiF5(NH3)], and Cs[SiF5(NH3)], as well as [NH4(NH3)(2)](2)[SiF6] and [Tl-2(NH3)(6)][SiF6]center dot 2NH(3), from the other starting materials and characterized them by either singlecrystal or powder X- ray diffraction. The compound [NH4(NH3)(2)](2)[SiF6] contains the very rarely observed hydrogen- bonded, C-2v-symmetric diammine ammonium cation [NH4(NH3)(2)](+), and the compound [Tl-2(NH3)(6)][SiF6]center dot 2NH(3) is an example for an uncommon Tl(I)-Tl(I) interaction. This "thallophilic" interaction was investigated with quantum-chemical methods.