Strategies for the Synthesis of Chiral Carbon‐Bridged Group IV ansa‐Metallocenes

This minireview provides a survey of the various synthetic approaches to chiral ansa‐metallocenes of Ti, Zr, and Hf containing a carbon‐based bridge. The individual strategies to install substitution patterns at either the cyclopentadienyl framework or the bridging unit are highlighted with focus on the progress made towards a direct preparation of single complex stereoisomers. The review further includes the discussion of potential problems such as the formation of undesired diastereomers, the threat of racemization of enantiopure material, and synthetic challenges originating from the synthesis, purification, and isolation of the target complexes. The review has been written with the goal in mind to facilitate the design and synthesis of new chiral ansa‐metallocene derivatives for emerging research areas in asymmetric catalysis and organometallic chemistry. The club of chiral sandwiches: Chiral carbon‐bridged ansa‐metallocenes of Ti, Zr, and Hf have made a tremendous impact on polymer synthesis, asymmetric catalysis, and organometallic chemistry. The diverse synthetic strategies to access these complexes are discussed in detail with emphasis on stereoselectivity, isolation and purification techniques.