Date on Master's Thesis/Doctoral Dissertation

5-2014

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemistry

Degree Program

Chemistry, PhD

Committee Chair

Grapperhaus, Craig

Committee Member

Noble, Mark E.

Committee Member

Burns, Christopher T.

Committee Member

Sumanasekara, Gamini

Committee Member

Zamborini, Francis P.

Subject

Reactivity (Chemistry)

Abstract

This thesis presents ligand centered reactivity studies of metal stabilized thiyl radicals in solution, solid, and gaseous phases for catalysis and sensing based applications. Chemical oxidation of tris(2-diphenylphosphinebenzenethiolato )ruthenate(II) [Ru -1]- with ferrocenium hexafluorophosphate in the presence of ethylene yields [Ru-1·C,H.]PF6, from addition of the alkene across cis sulfur sites. In the presence of base [Ru-1·C,H.]+ is selectively deprotonated at the pseudoequatorial proton on the carbon a to the sulfur trans to phosphorus, yielding the vinyl metallosulfonium derivative [Ru-1·C,H3]. "H and 31p NMR spectra of [Ru-1'C,H3 ] are temperature dependent, associated with inversion of the sulfur lone pair at the vinyl metallosulfonium. The activation energy for the fluxional process calculated using density functional theory (B3LYP jLANL2DZ+6-31g) of 14.36 kcaljmol is consistent with the experimentally determined value of 13.08 kcaljmol. Addition of hydrochloric acid to [Ru -1'C,H3 ] regenerates [Ru -1·C,H.]+. Addition of DCl confirms the selectivity of this reverse reaction. In presence of excess base, the vinyl metallosulfonium complex [Ru-1'C,H3 ] undergo C-S bond cleavage under refluxing conditions, yielding Soxygenated derivatives of [Ru-1]- and a functionalized organic product. In collaboration with Professor Hao Chen from Ohio University, the ligand-centered gas phase reactivity studies of [Ru-1]' are performed by mass spectrometry (MS) in conjunction with ion/molecule reactions. The addition reactions of [Ru-i]+ and its fragments with alkenes and dimethyldisulfide (via. characteristic CH3S· transfer) in the gas phase are indeed observed, indicating the preserved thiyl diradical core structure is responsible for the addition reaction. Similar thiolate complexes, including [Re-i] and [Ni-i], were also examined and the addition of ethylene was not observed indicating lower reactivities of [Re-i]+ and [Ni-i]+ in comparison to [Ru-i]+. In collaboration with Professor Francis P. Zamborini in University of Louisville, a highly selective chemiresistive ethylene sensor based on reversible and selective ligand-centred substrate binding to a metal-stabilized thiyl radical has been developed. The solid-state device efficiently differentiates between ethylene and other alkene analytes. The sensor is prepared by simple dropcast deposition of the complex as a film across a microgap gold electrode.

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