Synthesis, characterization and reactivity of nickel(II) complexes stabilized by an intramolecular hydrogen bonding network

Metalloenzymes are able to perform a wide variety of difficult chemical transformations in a highly selective and efficient manner. The ability of metal complexes to perform a particular chemical reaction is dependant on the properties of the primary and secondary coordination environments. Development of transition metal complexes that catalyze the formation of organic compounds in a selective and highly efficient manner is of interest to synthetic chemists. Advancement in this area of research requires studies aimed at developing ligands that will give desirable properties upon binding to a metal ion. Using interactions present in biological systems, the ligands in this study have been developed to investigate the effects of the primary coordination sphere as well as hydrogen bonding interactions on complex formation as well as reactivity.;Chapter 2 discusses the synthesis of terminal monomeric NiII-OH complexes with H41R. The hydroxo ligand is stabilized by two intramolecular hydrogen bonding interactions and the source of the hydroxo ligand was confirmed to be water. Attempts to deprotonate the Ni II-OH complex to form a NiII-oxo complex were unsuccessful. Treating the NiII-OH complexes with KOtBu afforded the alkoxide substituted product. NiII-siloxide complexes were isolated upon reaction of NiII-OH with K[N(TMS)2 ].;Chapter 3 features the synthesis of a series of Ni(II) complexes with H2pmb, which contains two carboxyamido units appended from pyridine rings. Four Ni(II) complexes were synthesized and structurally characterized. It was determined that the carboxyamido groups either provided intramolecular H-bonds or the carbonyl oxygen can bind directly to the metal center.;Chapter 4 explores the electrochemistry of the Ni(II) complexes characterized in Chapter 3. Based upon the observed reduction potentials, the reduction chemistry of [NiIIH2pmb(Cl)2] was explored. Further reactivity of the reduced species was also explored with dioxygen. Preliminary reactivity studies will also be discussed.