The Pauson-Khand reaction is notably accelerated by TEMPO. According to DFT calculations, TEMPO could trigger a radical, low-energy pathway for the reaction by facilitating the decarbonylation of doublet complexes arising either from a CO/nitroxide exchange or from nitroxide addition to a CO ligand.
![TEMPO-promoted Pauson-Khand reaction. Single-electron activation of cobalt carbonyl bonds?](https://www.iciq.org/wp-content/uploads/2014/03/TEMPO-promoted-Pauson-Khand_eng_noticies_articles_2005_15.gif)