New examples Of [C6F5Xe]+ salts of the weakly coordinating [BY41- (Y = CN, CF3, or C6F5) anions were synthesized by metathesis Of [C6F5Xe][BF4] with MI[BY4] (MI = K or Cs; Y = CN, CF3, or C6F5) in CH3CN at -40 degrees C, and were crystallized from CH2Cl2 or from a CH2CI2/CH3CN solvent mixture. The low-temperature (-173 degrees C) X-ray crystal structures of the [C6F5Xe]+ cation and of the [C6F5XeNCCH3](+) adduct-cation are reported for [C6F5Xe][B(CF3)(4)], [C6F5XeNCCH3][B(CF3)(4)], [C6F5Xe][B(CN)4], and [C6F5XeNCCH3][B(C6F5)(4)]. The [C6F5Xe]+ cation, in each structure, interacts with either the anion or the solvent, with the weakest cation-anion interactions occurring for the [B(CF3)(4)](-) anion. The solid-state Raman spectra of the [C6F5Xe]+ and [C6F5XeNCCH3](+) salts have been assigned with the aid of electronic structure calculations. Gas-phase thermodynamic calculations show that the donor-acceptor bond dissociation energy of [C(6)F(5)XeNCCH3]+ is approximately half that of [FXeNCCH3](+)- Coordination of CH3CN to IC6F5Xe]+ is correlated with changes in the partial charges on mainly Xe, the ipso-C, and N, that is, the partial charge on Xe increases and those on the ipso-C and N decrease upon coordination, typifying a transition from a 2c-2e to a 3c-4e bond.