Bio-Organometallic Chemistry, ansa-Metallocenes, and Frustrated Lewis Pairs: Functional Group Chemistry at the Group 4 Bent Metallocenes

Functional group chemistry at the group 4 bent metallocenes is still a challenge, due to the special features of these early-metal systems. Nevertheless, an increasing number of reactions and protocols is being developed for attaching organic functional groups at the bent-metallocene frameworks and for carrying out reactions with them. Here some bio-organometallic bent metallocene systems are discussed. Chemical transformations are presented and discussed, including olefin metathesis and even variants of the Mannich reaction. It is shown that intramolecular [2 + 2] cycloaddition reactions between alkenyl substituents at the Cp or indenyl rings under dynamic topochemical reaction control can lead to ansa-metallocenes. Frustrated Lewis pair chemistry provides tools, for example, for reduction reactions under very mild conditions.