Text

theses

ETD doctoral

Since the initial report of pincer complexes in the late 1960’s, much research has been undertaken to understand the reactivity and applicability of these complexes. This thesis aims to add to the rich knowledge of pincer complexes and the activation of small molecules to lead to interesting chemical transformations. Advantageously, the pincer framework can be easily adapted by changing different aspects of the ligand. The synthesis, characterization and reactivity of (Me-PCP)IrHn, in which the para position on the backbone of the catalyst has been changed from a hydrogen to a methyl group is reported. Finally, attempts to isolate the highly reactive 3-coordinate 14-electron (Me-PCP)Ir species are also addressed. Rather than isolation or observance of any active catalytic species proposed as a 14e-, agostic, solvated, or dimeric species, it has been found that the cyclometalation or C-H activation of the tbutyl group attached to one of the phosphorous atoms occurs readily. Characterization of cyclometalated complexes and an interesting cyclometalated insertion product is described. Two different mechanisms are proposed and discussed in relation to previously cited pathways for the formation of each complex. The knowledge of the activation and binding of oxygen as well as the reactivity of oxidants and isolation of reactive intermediates is limited. The synthesis and characterization of two (Me-PCP)Ir oxygen species is detailed via reaction with oxygen directly followed by a discussion of the reactivity with other oxidants. A combined experimental and computational study was completed to determine the binding energies for the addition of a variety of ligands to the metal center of (PCP)IrHCl, (PCP)IrH2, and the (PCP)Ir fragment. The thermodynamics were determined directly through equilibrium reactions and compared to values derived from DFT calculations utilizing a variety of functionals with good agreement. Finally, the activation of hydrazine and related compounds by the parent (PCP)IrH2 complex is achieved and leads to both dehydrogenation and hydrogenation of hydrazine by pincer iridium (PCP) type catalysts to synthesize N2, H2 and NH3. The reactivity of other pincer complexes for this reaction will be compared and a computationally calculated mechanism for both pathways will be discussed along with supporting experimental evidence.

ETD_5706

doi:10.7282/T3G15Z99

Ph.D.

Includes bibliographical references

by Kathleen Donohue Field

The author owns the copyright to this work.