Assessing the Reactivity of Cobalt(II) Amide Co(TMP)2 toward Unsaturated Organic Molecules

Typically regarded as strong Brønsted bases with low nucleophilicity, TMP metal amides (TMP = 2,2,6,6-tetramethylpiperidide) find widespread application in deprotonative metalation chemistry. While most examples employ s-block metal amides, Co(TMP)2 has also emerged as a powerful metalating reagent for the cobaltation of pyridines and fluoroarenes. Herein, we investigate the ability of this Co(II) metal amide to undergo insertion reactions into its Co–N bonds by assessing its reactivity toward a range of heterocumulenes and unsaturated organic molecules. Excellent stoichiometric control was achieved in reactions toward phenyl isocyanate, diphenyl ketene, and carbon dioxide, where one or two of the TMP groups can undergo insertion. Contrastingly, extending these studies to 4-methylacetophenone revealed the preference of this metal amide to act as a base to form the relevant enolate complex. The reactivity of Co(TMP)2 toward phenyl isocyanate, benzonitrile, and 4-methylacetophenone was contrasted with that of the classical Co(II) amide Co(HMDS)2, which shows, in most cases, a diminished nucleophilic power and lower selectivity.