Iron(ii) catalysts containing diimino-diphosphine tetradentate ligands and their synthesis

Abstract

New hexa-coordinate iron (II) complexes comprising compounds of formula (I) are described. These compounds comprise a tetradentate ligand with donor atoms comprising nitrogen and phosphorus. These complexes are shown for the first time to be useful catalysts for the hydrogenation of ketones, aldehydes, or imines to produce alcohols or amines, and the asymmetric hydrogenation of prochiral ketones or imines to produce non-racemic alcohols or amines. The source of the hydrogen can be hydrogen gas or a hydrogen-donating molecule such as isopropanol or hydrogen-donating mixture such as formic acid and an amine depending on the structure of the catalyst. In certain embodiments, the axial ligands on the catalyst comprise organonitrile ligands, carbonyl ligands, isonitrile ligands, or combinations thereof. The catalysts and the preparation thereof are disclosed. A reaction using phosphine and diamine precursors that is templated by the iron ion is the preferred route to the catalysts.