CO Fixation to Stable Acyclic and Cyclic Alkyl Amino Carbenes: Stable Amino Ketenes with a Small HOMO–LUMO Gap
Résumé
A quick fix: In contrast to cyclic diamino carbenes, stable alkyl amino carbenes react with CO to give stable ketenes (see scheme, top). Contrary to the acyclic versions, cyclic amino ketenes cannot escape from the destabilizing n–π donation of the nitrogen lone pair, which induces a diradical character and unusual optical and NMR spectroscopic properties.