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 [3]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 [3]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 [3]- and [4]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.

The syntheses and characterization of nitroacetylenes have been studied with

respect to their large-scale production, purification, and NMR spectra, respectively. The ¹³C NMR spectrum of 1-nitro-2-(trimethylsilyl)ethyne (18) evidenced ¹³C–¹⁴N coupling

between the alkynyl carbon and the attached nitrogen, in agreement with the previously reported spectrum of 1-nitroethyne (16). The multi-gram preparation of high purity 18 is described. A history of previous work with nitroacetylenes is reviewed.

The stabilization of nitroacetylenes as hexacarbonyl dicobalt alkyne complexes was investigated. In conjunction with appropriate oxidizers, such complexes were shown to be long-term storage media for free nitroalkynes. The syntheses and complete characterization of the first two nitroalkyne transition metal complexes, [μ-1-nitro-2(trimethylsilyl)ethyne-1,2-diyl]bis(tricarbonylcobalt)(Co–Co) (25) and [μ-1-nitroethyne1,2-diyl]bis(tricarbonylcobalt)(Co–Co) (26), are described. Phosphine derivatives of 25 were prepared and studied. The synthesis of [μ-1,2-dinitroethyne-1,2diyl]bis(tricarbonylcobalt)(Co–Co) (24) by direct ligation, transformation of functional groups on existing complexes, and nitration of such complexes was unsuccessful.

Complexes 25 and 26 were applied to the synthesis of organic molecules. While they did not yield cyclopentenones via the Pauson-Khand cyclization, they rendered benzene derivatives by the [2 + 2 + 2] cobalt-mediated cyclotrimerization. In addition to two nitroindanes and a nitrotetralin, several new trinitrobenzene isomers were made, all potential precursors to energetic materials. The X-ray crystal structure of one of these,

1,3,5-trinitro-2,4,6-tris(trimethylsilyl)benzene (325), showed a planar, but distorted aromatic ring.

An application of alkyne metathesis to 1,2-di(prop-1-ynyl)arenes, producing dehydrobenzannulenes, is described. An efficient method for selective Sonogashira couplings of bromoiodoarenes under conditions of microwave irradiation is also reported.