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Novel and Previously Reported Mono(imino)pyridine-based Nickel(II) Complexes Synthesis and Structural Determination and Novel Mono(imino)pyridine-based Nickel(II) Complex for Use as an Alkene Polymerization Catalyst

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Description: One novel and one previously reported mono(imino)pyridine ligand were synthesized with i -propyl and methyl substituents on the imino carbon atom, respectively. These ligands have the imino functionality on the 2-position of the pyridine ring and 2,6-dimethyl substituents on the N -aryl group. The i -propyl substituted mono(imino)pyridine ligand undergoes E/Z isomerism in solution at room temperature. The ligand has been characterized via extensive NMR studies ( 1 H NMR, 13 C NMR, variable temperature NMR, gCOSY 2D NMR, NOESY 2D NMR, and EXSY 2D NMR). The i -propyl substituted mono(imino)pyridine ligand has a slight preference for the Z isomer, whereas the methyl substituted mono(imino)pyridine favors the E isomer (with no evidence of the Z isomer). Both ligands have been complexed to NiBr 2 (DME) to form precatalysts for the polymerization of ethylene. The i -propyl substituted mono(imino)pyridine nickel(II) complex has successfully oligomerized ethylene at -20 °C to produce a 22-24 carbon n -alkane (verified by 1 H NMR and FTIR). DSC analysis of this oligomeric n -alkane is consistent with a range of oligomer molecular weights and branching. Optimization of ethylene oligomerization conditions and use of GC-MS for product monitoring and molecular weight determination is ongoing.
Language: English
Format: Degree Work