Abstract

Key challenges in the development of catalysts based on first row (“3d”) transition metals include the substitutional lability of the open shell species involved, the changes of spin states in the individual reaction steps as well as the potential competition of single electron transfer steps. Most reaction sequences involve almost exclusively paramagnetic catalysts and catalytic intermediates. These properties render mechanistic studies challenging and also require care in the design of stereodirecting ligands.

Recently, we have developed new chiral pincer (PmBOX, Boxmi,...) ligands¹ which have been used in a variety of enantioselective transformations including alkylations of β-ketoesters and their subsequent cyclization to spirolactones, as well as the trifluoromethylation and azidation of β-ketoesters as well as oxindoles.[2] Their iron(II) and manganese(II) complexes match the activity and selectivity of the most efficient noble metal catalysts for the hydrosilylation or hydroboration of ketones.

The focus of the lecture will be the elucidation of the catalytic reaction mechanisms, including radical reaction networks,[4] and the identification and characterization of the (frequently) paramagnetic species involved.