Expanding the chemistry of d(0) transition through redox-active ligands: Synthesis and reactivity studies of Group 4 metals with redox-active phenylenediamine and phenanthrenediamine ligands

This dissertation describes the reactivity of Group 4 metal complexes containing redox-active ligands. Fundamental studies focused on understanding the two-electron oxidation reactivity of Group 4 redox-active ligand complexes through halogen oxidative addition and group-transfer reactivity.;Chapter 1 provides an introduction to the characteristics of redox-active ligands and the first reports of ligand non-innocence. An overview of previously reported ligand-based small molecule activation is also presented.;Chapter 2 describes the syntheses and characteristics of three classes of redox-active ligands, aminophenol, 1,2-phenylenediamine and phenanthrene-9,10-diamine.;In Chapter 3, complexation of [Ar-ap] (2,4-di-tert-butyl-6-(3,5-dimethylphenylamido)phenolate), [tBuCH2-pda] (N,N'-di- neo-pentyl-1,2-phenylenediamide) and [Me3Si-pda] ( N,N'-di-trimethylsilyl-1,2-phenylenediamide) to zirconium(IV) affords new metal complexes with two coordinated redox-active ligands and provides a basis for comparative studies on the ability of the substituted redox-active ligand to regulate steric properties at the transition metal center. While the [Ar-ap] ligand provides little steric regulation to the metal center, both of the disubstituted [tBuCH2-pda] and [Me3Si-pda] ligands enable the isolation of coordinatively and electronically unsaturated transition metal complexes.;Chapter 4 focuses on the coordination chemistry of Group 4 metals containing one [pada] (N,N'-bis(aryl)-9,10-phenanthrenediamide) ligand and evaluation of the effects that ligand substitution has on the stability and reactivity of transition metal complexes. These complexes provide a basis for realizing bond-activation reactivity through low-coordinate metal complexes.;In Chapter 5, fundamental studies of oxidative addition were studied by reacting halogen oxidants with d0 Group 4 metal complexes containing redox-active ligands. Enabled by an overall two-electron ligand oxidation, halogen oxidation with [tBuCH 2-pda]2Zr afforded the oxidative addition product [ tBuCH2-disq]2ZrX2 (disq = N,N'-di-neo-pentyl-1,2-diiminosemiquinone), with each [tBuCH2-pda] ligand being oxidized by one electron. Oxidative addition of halogen oxidants to d0 Group 4 metal complexes containing the [pada] ligands was facilitated by a two-electron oxidation of [pada] to the neutral [padi] (padi = N,N'-bis(aryl)-9,10-phenanthrenediimine) ligand.;In Chapter 6 the synthesis of zirconium(IV) and titanium(IV) imido complexes containing redox active ligands and their reactivity towards C--H bond activation was explored. In order to expand on the well-known metathesis reactivity of Group 4 imido complexes beyond C--H bond activation, the redox-functionalities of the ligands were used to enable group-transfer reactivity through ligand-based oxidations.