Formation of M(CO)4+ (M=Co, Rh) by dissolution of neutral Co and Rh carbonyl clusters in strong acids under CO atmosphere

The dissolution of the neutral Co carbonyl cluster, Co2(CO)8, in HSO3F or magic acid (HSO3F · SbF5) under a CO atmosphere results in the formation of the Co(I) tetracarbonyl cation, [Co(CO)4]+(solv), and H2. The IR and Raman spectra for [Co(CO)4]+(solv) suggest a trigonal bipyramidal structure in which two CO ligands together with a solvent ligand are in the equatorial plane, and the two axial CO ligands are in a nearly linear alignment. No cobalt carbonyl complexes are formed in less acidic solution such as 96% H2SO4. The dissolution of Rh4(CO)12 in concentrated H2SO4, HSO3F or magic acid (HSO3F · SbF5) under a CO atmosphere leads to the formation of the square-planar Rh(I) tetracarbonyl cation, [Rh(CO)4]+, and H2, where Rh(0) is unusually oxidized to Rh(I) by H+.