Lee, John P.
Pienkos, Jared A.; Albu, Titus V.
University of Tennessee at Chattanooga
Place of Publication
Styrene can be produced directly from benzene and ethylene through an atom economical oxidative hydroarylation process. In this process, an electrophilic homogeneous transition metal catalyst activates the C-H bond in benzene. I propose to explore this reaction in two fronts: 1) the synthesis of electron-poor trans-spanning bidentate pyridine ligands and 2) the computational study of pyridine-functionalized bidentate diimines. The trans-spanning ligand will utilize either a Ru(II) or Co(III) metallohinge with cis-coordinated 2-ethynylpyridine ligands. The complex [(p-cym)Ru(PMe3)(C2-2-py)2] (1) where (p-cym = para-cymene and C2-2-py = 2-ethynylpyridine) can be prepared from (p-cym)Ru(PMe3)(Cl)2 and HC2-2-py in the presence of lithium bis(trimethylsilyl)amide (LiHMDS). Complex 1 has been characterized by 1H and 31P NMR spectroscopy where the 31P NMR chemical shift at 15.2 ppm confirmed when the alkynyl-pyridine ligands were attached, and the 1H NMR showed mirror symmetry which is consistent with the proposed complex. Pd(II) acetate was attempted to coordinate to 1 in a trans fashion to make [(p-cym)Ru(PMe3)(C2-2-py)2Pd(OAc)2], however this gave inconclusive NMR results. This reaction was extended to the electron-poor Co(III) to prepare [Cp*Co(PMe3)(C2-2-py)2] (2) where (Cp* = pentamethyl cyclopentadienyl anion) from [Cp*Co(PMe3)(I)2]. Additional ligand analysis involved density functional theory (DFT) calculations using the B3LYP functional in Gaussian 16 software to determine the ligand-donating ability of six bis-imine ligands. The electron-withdrawing character of bis-imine ligands has been linked to C-H activation in N,N′-bis-(pentafluorophenyl)-2,3-dimethyl-1,4-diaza-1,3-butadiene, and by replacing a fluorine with a nitrogen in N,N′-bis-(2,3,5,6-tetrafluoripyridine)-2,3-dimethyl-1,4-diaza-1,3-butadiene, the electronic density was localized on the pyridines leaving an electron poor imine region.
B. S.; An honors thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Bachelor of Science.
Activation (Chemistry); Organometallic compounds
Neglia, Sophia, "Synthesis, characterization, and reactivity of organometallic complexes for catalytic carbon-hydrogen bond activation" (2021). Honors Theses.