Stability of the metal configuration in chiral-at-metal half-sandwich compounds

Half-sandwich compounds with a three-legged piano-stool geometry are prominent examples of optically active chiral-at-metal complexes. In these compounds, the configuration at the metal atom may be stable or labile in solution. Configurationally stable compounds can be used for the elucidation of the stereochemical course of substitution reactions and for organic synthesis in ligand transformation reactions. With configurationally labile compounds, the rate of change of the metal configuration can be measured, which sets an upper Limit with regard to the handling of the compounds in solution. Surprisingly in a number of recent papers the lability of the metal configuration has been overlooked resulting in misinterpretations and wrong conclusions.