The Lithocene Anion and “Open” Calcocene–New Impulses in the Chemistry of Alkali and Alkaline Earth Metallocenes

The resurgence of the C5 ligand in main group chemistry: Recently Harder et al. (Angew. Chem. Int. Ed. Engl. 1994, 33, 1744) have synthesized and structurally characterized the lithocene anion 1, the simplest sandwich complex, and Hanusa et al. (Angew. Chem. Int. Ed. Engl. 1994, 33, 2191) have prepared the “open” calcocene 2, an alkaline-earth metal complex with a remarkable structure. Such compounds are not only of significance for bonding theory, they are also interesting as precursors for important industrial processes.