Cobalt and Nickel-Based Organometallic Chemistry of the [N]Phenylenes
This dissertation explores the synthesis and study of linear [N]phenylene cobalt complexes and the reactions of angular [N]phenylenes with nickel catalysts. Chapter 1 contains a general introduction to the properties of the [N]phenylenes as well as a brief overview of earlier organometallic [N]phenylene chemistry with an emphasis on work directly related to that presented in the subsequent chapters.
Chapter 2 presents studies regarding first ever examples of photo-induced, thermally reversible haptotropic shifts in linear phenylene cyclopentadienyl cobalt (CpCo) complexes. In these reactions, the CpCo fragment migrates from one cyclobutadiene ring to another upon exposure to UV irradiation. Heating the photoisomer complexes causes the metal fragment to return to its original position. Aside from the novelty of an eta-4:eta-4 cyclobutadiene migration, the photo-induced, thermally reversible nature of these systems makes them attractive as candidates for photostorage devices and/or molecular switches. The syntheses and structural studies of the linear phenylene(CpCo) complexes are discussed. In addition to the experimental work, computational studies on the haptotropic shift are also included. Closely related work, such as the observation of an intermediate haptotropic species at low temperature and the preparation of a linear phenylene complex containing two CpCo units bound to the ligand, is also discussed.
Chapter 3 describes nickel-catalyzed insertion reactions with angular phenylenes as a method for preparing derivatives of [N]phenacenes, a class of polycyclic aromatic hydrocarbons that are of interest in organic electronic applications. Previous work regarding nickel insertion reactions with biphenylene is mentioned. Nickel-catalyzed insertion reactions with angular - and phenylene are then described. Mechanistic studies, both experimental and computational, are discussed. The results from these studies were used to optimize the reaction to produce [N]phenacenes as the major products of these insertion reactions.
Chapter 4 contains experimental details relating to chapters two and three. General experimental considerations, synthetic procedures, crystallographic, and computation data are presented. Relevant references are also included in this chapter.