The selective reaction of α-olefins with two ethylene molecules

• Applicant: Professor Dr. Rhett Kempe
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 518769132

General remarks. α-Olefins are important starting materials for the synthesis of plastics, pharmaceuticals, bulk and fine chemicals. The synthesis of α-olefins from ethylene, an inexpensive and abundantly available C2 building block, is carried out in mega-ton scale annually and represents one of the most important application of homogeneous catalysis in the chemical industry. The selective synthesis of α-olefins from ethylene is restricted to only three olefins: 1-butene, 1-hexene, and 1-octene. All three are extremely important and applied diversely. Other synthesis protocols produce distributions of α-olefins that need to be separated. The interest of a specific olefin rarely matches with its share or proportion in the product distribution. A broadly applicable α-olefin elongation reaction, in which α-olefins react selectively with ethylene, would be highly desirable. In addition, the introduction of branches is attractive with regard of the synthesis of artificial lubricants. Furthermore, branched α-olefins are monomers for the synthesis of transparent plastics and as membranes for gas separation. Selectively branched α-olefins can also be of interest for functionalization reactions such as hydroformylation, a reaction carried out in mega-ton scale. Preliminary work. In published preliminary work, which appeared in “Science” and “Nature Communication”, we introduced novel catalytic α-olefin syntheses. The elongation and branching of α-olefins is conceptually especially interesting since it permits the selective synthesis of various α-olefins and in comparison to established synthesis of α-olefins from ethylene access to branched α-olefins is provided for the first time. Aims and work plan. The central intension of our proposed works are: Understanding the discovered reaction of α-olefins with two ethylene molecules specifically the ethylene- α-olefin-ethylene sequence mechanistically (mechanism) and to explore the potential of this reaction for the synthesis of α-olefins (olefin synthesis). Therefore, seven work packages are proposed that are related to the two main intentions. Mechanism. WP 1: experimental work to understand the insertion sequence. WP 2: variation of the central metal. WP 3: variation of the ligands. Olefin syntheses. WP 4: co-dimer selectivity of other Ap-Imi-Ti complexes. WP 5: tetramerisation of ethylene towards a branched octane. WP 6: polymerization and co-polymerization of ethylene 4-ethylhexene. WP 7: selective reactions of dienes with ethylene. The proposed milestones are listed in section 2.3.3. Both central aims are strongly connected and a conceptually novel quality of knowledge can only be obtained in “dialogue”.

• DFG Programme: Research Grants