Ligand Design Strategies for Regulating Small Molecule Binding and Reactivity at Transition Metal Centers Open Access

Abstract

Ligand design is an area of great interest to chemists. With respect to coordination chemistry, ligands may be tailored sterically, electronically, and through installation of functionalities that make up the secondary coordination sphere of the transition metal ion. In Chapter 2 of this dissertation, the synthesis of a series of tetradentate ligands that vary in the electronic character of the aromatic acyl substituent is described. Cobalt(II) complexes of these ligands were prepared, and their synthesis and characterization will also be discussed. The cyanide binding properties of these complexes were explored, and it was found that the complexes with the most electron- withdrawing substituents not only effect the most electron-poor cobalt center, but they also appear to effect a type of secondary interaction between the bound cyanide and the aromatic rings that has not yet been described in the literature. In Chapter 3, the synthesis, characterization, and reactivity of iron(II) complexes that utilize similar ligands will be explored. Several of the complexes with electron-rich aromatic acyl substituents have proven to be effective catalysts for N-methyl C-H bond activation. The catalytic activity and proposed mechanism of action will be discussed. A byproduct of this reaction, a rare, terminal Fe(II)-hemiaminate species was isolated, and its characterization will also be discussed. In Chapter 4, the synthesis, characterization, and reactivity of cobalt(II), copper(I), and zinc(II) complexes of a neutral, tridentate ligand will be described. These complexes have the potential to be useful as low coordinate, reactive transition metal complexes.

Table of Contents

Table of Contents
Chapter 1 Ligand Design Strategies for Regulating Small Molecule Binding and
Reactivity at Transition Metal Centers………………………………………..1
Section 1-1 Introduction……………………………………………………………………….1
Section 1-2 Utility of Ligand Design in Tetradentate Triamidoamine Ligands………………2
Section 1-3 Ligand Design in Tetradentate Tris(carboxamide)amine Ligands……………….8
Section 1-4 Dissertation Overview…………………………………………………..............11
Chapter 2 Utilizing Aromatic Substituents for Regulation of Cyanide Binding by
Cobalt(II) Metal Complexes…………………………………………………..16
Section 2-1 Introduction……………………………………………………………………...16
Section 2-2 Results and Discussion………………………………………………………….26
Section 2-2-1 Synthesis of Trigonal Monopyramidal and Solvento Cobalt(II)
Complexes………………………………………………………………………27
Section 2-2-2 Structural Characterization of Trigonal Monopyramidal and Solvento
Cobalt(II) Complexes…………………………………………………………...31
Section 2-2-3 Cyanide Binding………………………………………………………………...37
Section 2-2-4 Electrochemistry and Alkyl-Substituted Complexes…………………………...49
Section 2-3 Conclusion……………………………………………………………………...54
Section 2-4 Experimental Section…………………………………………………………...56
Chapter 3 Biomimetic Aerobic Oxidation of N-alkyl C-H Bonds by a
Non-heme Iron(II) Catalyst…………………………………………………...89
Section 3-1 Introduction……………………………………………………………………..89
Section 3-2 Background and Significance……………………………………………….…..94
Section 3-2 Results and Discussion………………………………………………………...100
Section 3-3 Conclusion……………………………………………………………………..130
Section 3-4 Experimental Section………………………………………………….............130
Chapter 4 Use of a Neutral, Tridentate Ligand for Stabilization of Low
Coordinate Transition Metal Complexes…………………………………...154
Section 4-1 Introduction…………………………………………………………………….154
Section 4-2 Results and Discussion………………………………………………………...161
Section 4-3 Conclusion……………………………………………………………..............177
Section 4-4 Experimental Section…………………………………………………………..178

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School	Laney Graduate School
Department	Chemistry
Degree	PhD
Submission	Dissertation
Language	English
Research Field	Chemistry, Inorganic
Keyword	C-H bond activation anion binding iron complexes cobalt complexes
Committee Chair / Thesis Advisor	MacBeth, Cora E., Emory University
Committee Members	Hill, Craig L, Emory University Gallivan, Justin, Emory University

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