Book excerpt: The conversion of hydrocarbon resources (oil and natural gas) to useful products constitutes a major portion of industrial chemistry; wherein, the products of such processes are utilized in the manufacture of materials, commodity chemicals, and pharmaceuticals. One possible method for overcoming this challenge is the design of new catalysts that operate via the C-H activation reaction coupled to an efficient M-R functionalization using transition metal catalysts. However, very few efficient C-H functionalization catalysts have been reported in the literature. The development of new methods to functionalize M-R intermediates and their coupling to C-H activation may meet this challenge. This thesis presents work focused on two core areas related to C-H bond functionalization, C-H activation and M-R functionalization. C-H activation involves the formation of an activated of metal-carbon intermediate by scission of a hydrocarbon C-H bond. This is followed by functionalization of the incipient metal-carbon intermediate to generate C-X bonds. The concepts related to choosing such a two-step, C-H activation/M-R functionalization, approach are presented in Chapter 1. Following chapters focus on independent study of C-H activation and M-R functionalization reactions, with a final emphasis on combining working M-R functionalization reactions to known C-H activation catalysts to complete the catalytic cycle. Chapter 2 focuses on Baeyer-Villiger and related functionalization reactions of an aryl-rheniumtrioxide complex. Work on M-R functionalization reactions is extended in Chapter 3 with a study on low oxidation state Re-CH3 compounds for oxy-functionalization reactions. Examination of an iridium catalyst that undergoes extraordinarily facile C-H activation and the mechanistic basis for the observed catalytic rates is presented in Chapter 4. Chapter 5 extends our examination on the C-H activation reaction using iridium and rhodium catalysts and finds that both arenes and alkanes are activated. Most significantly, oxy-functionalization of benzene is observed in the presence of Cu II salts using either family of catalysts. Finally, Chapter 6 makes concluding remarks on this work and what lies in store for the future.