Synthesis of a Series of Mono(imino)pyridines and Synthesis of and Computational Studies on Carbon1-Symmetric Bis(imino)pyridine Ligands

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Description: A series of novel mono(imino)pyridine ligands with t -butyl, phenyl, and methyl substituents on the imino carbon were synthesized and characterized through 1 H NMR, 13 C NMR, gCOSY, and NOESY spectroscopy. Variable temperature 1 H NMR data was obtained for each mono(imino)pyridine ligand in various NMR solvents in order to determine solvent effects on E/Z isomer ratios. Full characterization of the E/Z conformers of these mono(imino)pyridines in varied NMR solvents is ongoing. These mono(imino)pyridines and their precursors were used as starting materials in attempted syntheses of two C 1 -symmetric bis(imino)pyridine ligands. These target bis(imino)pyridine ligands include a t -butyl substituent on one imino carbon and either a phenyl or methyl group on the other imino carbon. These targets would be the first reported examples with different groups on each imino carbon. Asymmetric bis(imino)pyridine ligands such as these are anticipated to catalyze ethylene polymerization upon metalation with iron(II) in the presence of MAO. It is also suggested that the asymmetry of these ligands could afford utility for catalytic alternating copolymerization of ethylene and α-olefins. Attempts were made to synthesize both target bis(imino)pyridine ligands using three different synthetic routes: lithium-halogen exchange, Grignard reaction, and Negishi cross-coupling. Computational studies were performed on both target ligands in order to predict the lowest energy conformers and NMR chemical shift values. The search for a successful synthetic route for these bis(imino)pyridine ligands is ongoing.
Language: English
Format: Degree Work