Take a “Snapshot” of New Syntheses, Reactions, and Characterizations from Unusual Unsaturated Ring Strained Group 4 Metallacycles

Abstract

Recently published syntheses, reactions and characterizations of unusual unsaturated ring strained Group 4 metallocene metallacycles like metalla‐cyclocumulenes, ‐cycloallenes and ‐cycloalkynes with different ring size are updated for the last three years. There exist for some of these metallacycles, depending on the ring size, 7‐, 5‐ and 4‐membered compounds. The new results for these metallacycles are summarized here and considered in addition to the former published results. Additionally, several compounds of this type were now characterized by new reactions. For a better understanding of these compounds, some spectroscopical methods as well as theoretical calculations were published. Despite of these all‐C‐metallacycles, only in some cases the syntheses and reactions for the corresponding hetero‐metallacycles were published too. Examples for these metallaheterocyclic compounds will not be considered in this article. All these unusual ring strained compounds have a great potential for a lot of interesting synthetic applications in the future. Additionally, they are very interesting from the theoretical point of view.

Cp2Ti(II) Mediated Rearrangement of Cyclopropyl Imines

“…The titanocene framework has provided an excellent platform for the study of titanacycles and their chemistry. , Many 6-membered, C- and N-coordinated unsaturated titanacycles have been studied; generally, 5- or 6-membered titanacycles can be formed through insertion of alkyne or nitrile into smaller 3- or 4-membered titanacycles or through reaction of carbodiimides with a “Cp 2 Ti II ” source. − There have been no reports of the isolation of azatitanacycles similar to IM1 . We envisioned that the synthesis of this azatitanacycle on the titanocene framework would provide a good platform for further studies of its reactivity in the context of the catalytic reaction. − …”