Phosphinine- and Phosphacyclohexadienyl-Complexes: Novel Phosphorus Compounds for the Activation of Small Molecules and for Homogeneous Catalytic Reactions

Building on a successful first funding period, the joint project between the Wolf (University of Regensburg) and Müller (Free University of Berlin) research groups will be continued into the next phase. This research project focuses on the Hückel-aromatic λ3σ2-phosphinines (phosphabenzenes), which are the higher homologues of pyridines. Due to their diverse coordination modes and good π-acceptor properties, these ligands exhibit an extremely versatile coordination chemistry. In particular, they are highly suitable for the stabilization of low-oxidation state transition metal complexes, relevant for small molecule activation homogeneous catalysis. Furthermore, phosphinines can be converted into anionic 1-R-phosphacyclohexadienyls by reaction with organolithium or Grignard reagents, which are also of interest as ligands for transition metals. Phosphinines and their derivatives can thus be used to access unusual metal complexes and metal clusters. In the course of the first funding period, many of the originally postulated ideas for the synthesis and reactivity of phosphinine-based transition metal complexes or phosphacyclohexadienyl anions were successfully implemented. The diversity of the results promises a very multifaceted chemistry in the second phase, where, in addition to further research into the basic coordination chemical properties, applications in the field of (asymmetric) catalysis will be particularly in the focus. The following major aims will be pursued: i) development of bi- and tridentate phosphinines as well as chiral phosphinines and their coordination compounds; ii) activation of small molecules with phosphinine-based Co- and Fe-complexes iii) cobalt-catalyzed hydroformylation and hydrogenation reactions; iv) hydrofunctionalization reactions with axially-chiral 1-R-phosphacyclohexadienyl anions. The expertise of our two research groups (AK Wolf: synthesis, handling and application of highly reactive metallate anions; AK Müller: synthesis, reactivity, coordination chemistry and application of functionalized phosphinines) will be crucial for the successful implementation of these planned extensive studies in the second funding period.