Term of Award

Winter 2025

Degree Name

Master of Science, Applied Physical Science

Document Type and Release Option

Thesis (open access)

Copyright Statement / License for Reuse

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Department

Department of Chemistry and Biochemistry

Committee Chair

Michele McGibony

Committee Member 1

Brandon Quillian

Committee Member 2

Clifford Padgett

Committee Member 3

Jose Jimenez

Abstract

This study investigates: 1) the synthesis and reactivity of the mono- substituted systems, [κ²-(t-bipy)Ru(NCMe)2(Ph)(PR3)][BArF'] supported by different ancillary ligands PR3 = (P(OCH3)3 and P(CH3)3) and a single bidentate ligand, 4,4′-di-tert-butyl-2,2′-bipyridine (t-bipy), and 2) UV/heat formation of di-PR3 and tri-PR3 systems supported by a single bidentate ligand to better understand the mechanism of styrene production. Utilizing [(η6-p-cymene)RuI(µ-I)]2 (1), the complexes (η6-p-cymene)RuI2(P(OCH3)3) (2) and (η6-p-cymene)RuI2(P(CH3)3) (3) were synthesized and phenylated to produce (η6-p-cymene)RuI(Ph)(PR3) (6; PR3 = P(OCH3)3 and 7; PR3 = P(CH3)3). Complex 4, (η6-p-cymene)RuCl2(P(CH3)3), was also synthesized and phenylated to produce (η6-p-cymene)RuClPh(P(CH3)3) (5) to understand the impact of chloride versus iodine ligands in the phenylation reactions. Heating 6 and 7 in acetonitrile afforded the tetra-acetonitrile Ru(II) complexes, [(NCMe)4Ru(Ph)(PR3][I] (8; PR3 = P(OCH3)3 and 9). Complexes 8 and 9 undergo clean exchange of the acetontrile ligands upon reaction with 4,4′-di-tert-butyl-2,2′-bipyridine (t-bipy) to yield [κ2-(t-bipy)Ru(NCMe)2(Ph)(PR3)][I] (10; PR3 = P(OCH3)3 and 11; PR3 = P(CH3)3). The iodide counterion of 10 and 11 can be exchanged with BArF' counter anions to produce [κ2-(t-bipy)Ru(NCMe)2(Ph)(PR3)][BArF'] (12; PR3 = P(OCH3)3 and 13; PR3 = P(CH3)3). Catalytic olefin hydroarylation was evaluated under various conditions (additive, pressure, heat, and time) with styrene turnover numbers (TONs) quantified by GC-MS. Catalytic evaluation demonstrated a pronounced preference for styrene formation over ethylbenzene, with turnover numbers increasing under elevated temperatures and ethylene pressure, in the presence of acetonitrile (3.29 mmol styrene per mmol catalyst for 13 and 2.87 mmol styrene per mmol catalyst for 12 at 120 °C, 50 psi, 72 h). Cyclic voltammetry of 12 and 13 revealed a Ru(III/II) redox potential of +0.371 V and +0.155 V, respectively. Photochemical and thermal substitution studies revealed interesting substitution patterns with 12 and 13, wherein under thermal conditions the complexes undergo a Berry psuedo-rotation (BPR) causing the phenyl to reorganize to a position orthogonal to the bipy plane, while under photochemical reactions showed no BPR. Under photochemical conditions, tri-phosphine/phosphite complexes were isolated with the phosphorus ligands arranged in a meridional fashion. Under heated conditions, the P(OMe)3 complex 12 yielded a di-phosphite complex, while with 13, the PMe3 complex, resulted in the phosphine ligands arranged in a facially-coordinating fashion. The difference in their reactivity is largely driven by steric factors. It was found that the stronger σ-donors such as P(CH3)3 enhanced catalytic turnover. All complexes were characterized by multinuclear NMR spectroscopic methods (1H, 13C, 31P, 19F), and several were structurally confirmed by single-crystal X-ray diffraction (2, 3, 6, 7, 10, and 13). The structures of 10 and 13 were assigned using advanced 2D NMR technique (HSQC).

Research Data and Supplementary Material

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