Organometallic Chemistry and Catalysis

Organometallic Chemistry and Catalysis

Our research is directed toward the preparation of reactive transition metal complexes for stoichiometric and catalytic applications. We focus our attention on the development of new chiral and non-chiral auxiliary ligand systems which are able to bind, activate and functionalize the substrates at the metal center. The ultimate goal of the research program is to identify new ligand families and their corresponding metal complexes for new, more selective or more widely applicable catalytic transformations.

State-of-the-art routine lab equipment will be made available and includes synthetic aspects of the project (Schlenk-line techniques, Glovebox techniques) as well as analytical aspects (GC-MS, GC-FID's and HPLC instruments with chiral stationary phases within the laboratory, NMR and X-ray analysis and other necessary equipment within the department).

 

Ligand Systems Based on Chiral Sulfoxides and Their Use in Late-Metal Chemistry and Catalysis

Expanding the ligand families capable of acting as successful entities in metal-mediated reactivity and catalysis is crucial for future discoveries in this field and will lead to systems that show unprecedented reactivity patterns. One of our recent research goals is to identify and apply chiral chelating sulfoxides as sulfur-based ligands in late-transition metal chemistry. First results show that these ligands indeed are able to perform well in a conjugate addition reaction catalyzed by Rhodium. The honours projects available in this area of our research will focus on novel ligand systems of this family and will expand catalytic reactivity to other reactions catalyzed by late-transition metals. For additional information on our research, please consult the following publications: R. Mariz et al., J. Am. Chem Soc. 2008, 130, 2172; J. J. B├╝rgi et al., Angew. Chem. Int. Ed. 2009, 48, 2768; R. Mariz et al., Chem. Eur. J. 2010, 16, 14335; G. Sipos et al., Chem. Soc. Rev. 2015, 44, 3834; Zhao et al., Adv. Synth. Catal. 2016, 358, 1759.

 

New Chiral N-Heterocyclic Carbene Ligands in Asymmetric Catalysis

Reactions incorporating NHC metal complexes represent some of the most significant advances in homogeneous catalysis during the last decade, particularly for alkene metathesis and for coupling reactions. Nevertheless, there is a very restricted architectural choice for these ligand system and this is particularly hindering development of chiral monodentate NHCs. In the last few years, we have therefore initiated a research program that proposes the synthesis of new classes of monodentate, chiral NHCs that incorporate substituted naphthyl sidechains on the nitrogen atoms. In doing so, we are indirectly relying on a very successful design motif in chiral ligand synthesis that goes back to Noyori’s bis-phosphine ligand BINAP. These new types of ligand systems will allow for the synthesis of new transition metal complexes, where our focus will particularly lie on the isolation of highly unsaturated precatalysts. Special emphasis in subsequent applications will be put on the identification of more active chiral rhodium and iridium NHC compounds in catalysis, development of better asymmetric nickel, palladium and ruthenium mediated transformations and the development of unknown NHC-Ag catalysis. For preliminary data from our group on this project, see: X. Luan et al., Org. Lett. 2008, 10, 5569; X. Luan et al., Org. Lett. 2010, 12, 1912; L. Wu et al., Angew. Chem Int. Ed. 2012, 51, 2870; Sipos et al., Chem. Eur. J. 2016, 22, 6939.

 

New Catalysts and New Substrates for Ruthenium-catalysed Olefin Metathesis Reactions

Olefin metathesis has experienced a significant evolution in the last decades and is becoming one of the most useful synthetic transformations for generating carbon-carbon double bonds. The reaction can be applied in a great variety of synthetically useful permutations that include ring-closing metathesis (RCM), cross metathesis (CM) and enyne metathesis. Among the catalysts that have been developed, ruthenium alkylidene complexes incorporating an N-heterocyclic carbene (NHC) ancillary ligand (Grubbs’ second-generation catalyst) have become the most widely used in organic synthesis. The goal of this project is twofold; we have already been able to show that modifying the NHC ligand (see project 2) can bring about a clear increase in catalyst performance; further fine-tuning is therefore a worthwhile target and is also expected to lead to new reactivity in difficult or novel applications of the metathesis reaction. Indeed, metathetical reactivity of relatively electron-rich double bonds is still very challenging, presumably due to the fact that stable, Fischer-carbene type complexes are generated upon reaction with the catalyst’s metal center. Here, new results in our group have shown that modification of the substrates themselves might lead the way to exploiting metathesis reactions that have previously not been known. For recent results from our group, see: X. Luan et al., J. Am. Chem. Soc. 2008, 130, 6848; M. Gatti et al., J. Am. Chem. Soc. 2009, 131, 9498; M. Gatti et al., J. Am. Chem. Soc. 2010, 132, 15179.