Homoleptic octahedral, superelectrophilic sigma-bonded metal carbonyl cations of the type [M(CO)(6)](2+) (M = Ru, Os) are generated in the Bronsted-Lewis conjugate superacid HF/SbF5 by reductive carbonylation Of M(SO3F)(3) (M = Ru, Os) or OsF6. Thermally stable salts form with either [Sb2F11](-) or [SbF6](-) as anion, just as for the previously reported [Fe(CO)(6)](2+) cation. The latter salts are generated by oxidative (XeF2) carbonylation of Fe(CO)(5) in HF/ SbF5. A rationale for the two diverging synthetic approaches is provided. The thermal stabilities Of [M(CO)(6)][SbF6](2) salts, studied by DSC, range from 180 degrees C for M = Fe to 350 degrees C for M = Os before decarbonylation occurs. The two triads [M(CO)(6)][SbF6](2) and [M(CO)(6)][Sb2F11](2) (M = Fe, Ru, Os) are extensively characterized by single-crystal X-ray diffraction and vibrational and C-13 NMR spectroscopy, aided by computational studies of the cations. The three [M(CO)(6)][SbF6](2) salts (M = Fe, Ru, Os) crystallize in the tetragonal space group P4/mnc (No. 128), whereas the corresponding [Sb2F11](-) salts are monoclinic, crystallizing in space group P2(1)/n (No. 14). In both triads, the unit cell parameters are nearly invariant of the metal. Bond parameters for the anions [SbF6](-) and [Sb2F11](-) and their vibrational properties in the two triads are completely identical. In all six salts, the structural and vibrational properties of the [M(CO)(6)](2+) cations (M = Fe, Ru, Os) are independent of the counteranion and for the most part independent of M and nearly identical. Interionic C center dot center dot center dot F contacts are similarly weak in all six salts. Metal dependency is noted only in the C-13 NMR spectra, in the skeletal M-C vibrations, and to a much smaller extent in some of the C-O stretching fundamentals (A(1g) and T-1u). The findings reported here are unprecedented among metal carbonyl cations and their salts.