Dynamic 13C NMR studies of ligand exchange in linear (d10) silver(I) and gold(I) and square-planar (d8) rhodium(I) homoleptic metal carbonyl cations in superacidic media.

The dynamic CO exchange of the monovalent metal carbonyl cations [Ag(13CO)]+, [Au(13CO)2]+–Au(13CO) SO3F and [Rh(12CO)4−x(13CO)x]+ (x⩽1) in superacidic solutions was studied by variable-temperature 13C NMR methods. The exchange rates are strongly dependent on the acidity of the solvent, the concentration of metal carbonyl cations and temperature. Whereas a suitable exchange rate of the Ag(I) system is only accessible in magic acid (HSO3F–SbF5), the more stable Au(I) and Rh(I) systems were studied in the less acidic fluorosulfuric acid. Selected solutions of Ag(I), Rh(I) and Au(I) yielded activation barriers ΔG* of 42.7, 43.5, and 56.2 kJ mol−1 respectively. Copyright © 2005 John Wiley & Sons, Ltd.