Studies on the cyclometallation of ferrocenylimines

This review describes the cyclometallation reaction, including cyclomercuration, cyclopalladation and cycloplatination of Schiff base type of ferrocenylimines as well as the transmetallation reaction of cyclometallated ferrocenylimines and the stereochemistry associated with these reactions. The applications of cyclopalladated ferrocenylimines in several fields are also demonstrated in this review. The molecular and crystal structures of the products as well as the absolute configurations of optically active products were established by X-ray diffraction, NMR techniques, IR, UV–vis, etc. The general features of these reactions, especially the regioselectivity and the reaction mechanisms, are discussed. In addition, the structure–property relationships are discussed throughout this investigation. The transmetallation of optically pure cyclometallated ferrocenylimines with other metals such as mercury, tin and tellurium was found to proceed with complete retention of stereochemistry. This discovery led to a convenient method for the synthesis of optically pure cyclometallated organic compounds that are difficult to prepare by using conventional methods. Accordingly, a number of cyclometallated ferrocenylimines have been prepared in optically pure forms, which display surprisingly high angles of rotation.