Formation of a Unique ansa‐Metallocene Framework by Intramolecular Photochemical [2+2] Cycloaddition of Bis(2‐alkenylindenyl)zirconium Complexes

Complexes with backbone: Upon photolysis the title complexes undergo intramolecular [2+2] cycloaddition to yield unique cyclobutylene-bridged ansa-zirconocenes. The annelated phenylene rings of the indenyl ligand lie directly above and below the σ ligands of the bent metallocene wedge (see picture). Ligands that are introduced inside the resulting “phenylene π-electron box” display special chemical and spectroscopic features.