Steve Ritter’s entertaining article, “End of the Innocence for Cyclopentadienyl” (C&EN, June 13, page 6), about transition-metal complexes containing the η5-pentamethylcyclopentadienyl (or Cp*) ligand prompts me to remind readers that the activation of ring methyls in Cp* complexes of rhodium, iridium, and especially ruthenium was described in many papers in the 1980s and 1990s (J. Am. Chem. Soc. 1994, DOI: 10.1021/ja00080a050; Organometallics 1998, DOI: 10.1021/om970994a; and J. Chem. Soc. Chem. Commun. 1989, DOI: 10.1039/c39890000105).
Though this methodology is very useful for the synthesis of a wide variety of η5-C5Me4Z complexes, the downside is sometimes, as Ritter notes, the loss of the protecting ligand, which can lead to the destruction of the complex and the loss of the activity.
However, all catalysts, be they organic, organometallic, inorganic, or biological, do eventually decay with loss of activity. The key to success is to keep the catalyst alive through as many cycles as possible.
July 4, page 13: A news story about the start-up Modern Meadow should have stated that the company calls its product biofabricated leather, not cultured leather. In addition, contrary to what the story and an outside analyst said, the company says its process is animal-free. Lastly, a quote attributed to Modern Meadow Chief Executive Officer Andras Forgacs should have been attributed to Chief Technology Officer David Williamson.