Homoleptic octahedral, superelectrophilic
![](/images/gifchars/sigma.gif)
-bonded metal carbonyl cations of the type [M(CO)
6]
2+ (M = Ru, Os)are generated in the Br
![](/images/entities/oslash.gif)
nsted-Lewis conjugate superacid HF/SbF
5 by reductive carbonylation of M(SO
3F)
3 (M =Ru, Os) or OsF
6. Thermally stable
salts form with either [Sb
2F
11]
- or [SbF
6]
- as anion, just as for the previouslyreported [Fe(CO)
6]
2+ cation. The latter
salts are generated by oxidative (
XeF2) carbonylation of Fe(CO)
5 in HF/SbF
5. A rationale for the two diverging synthetic approaches is provided. The thermal stabilities of [M(CO)
6][SbF
6]
2salts, studied by DSC, range from 180
![](/images/entities/deg.gif)
C for M = Fe to 350
![](/images/entities/deg.gif)
C for M = Os before decarbonylation occurs. Thetwo triads [M(CO)
6][SbF
6]
2 and [M(CO)
6][Sb
2F
11]
2 (M = Fe, Ru, Os) are extensively characterized by single-crystalX-ray diffraction and vibrational and
13C NMR spectroscopy, aided by computational studies of the cations. Thethree [M(CO)
6][SbF
6]
2 salts (M = Fe, Ru, Os) crystallize in the tetragonal space group
P4/
mnc (No. 128), whereasthe corresponding [Sb
2F
11]
- salts are monoclinic, crystallizing in space group
P2
1/
n (No. 14). In both triads, the unitcell parameters are nearly invariant of the metal. Bond parameters for the anions [SbF
6]
- and [Sb
2F
11]
- and theirvibrational properties in the two triads are completely identical. In all six
salts, the structural and vibrational propertiesof the [M(CO)
6]
2+ cations (M = Fe, Ru, Os) are independent of the counteranion and for the most part independentof M and nearly identical. Interionic C···F contacts are similarly weak in all six
salts. Metal dependency is notedonly in the
13C NMR spectra, in the skeletal M-C vibrations, and to a much smaller extent in some of the C-Ostretching fundamentals (A
1g and T
1u). The findings reported here are unprecedented among metal carbonyl cation
sand their
salts.