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, Co-2(CO)(8), in HSO3F o r magic acid (HSO3F . SbF5) under a CO atmosphere results in the formation of the Co(I) tetracarbonyl cation, [Co(CO)(4)]((solv))(+), and H-2. 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 th e equatorial plane, and the two axial CO ligands are in a nearly linear ali gnment. No cobalt carbonyl complexes are formed in less acidic solution suc h as 96% H2SO4. The dissolution of Rh-4(CO)(12) in concentrated H2SO4, HSO3 F 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 H-2, where Rh(0) is unusually oxidized to Rh(I) by H+. (C) 2000 Elsevier Science S.A. All rights reserved.