Recent research has shown ring-slip processes to be important in the photochemistry of organometallic complexes of the type (r|6-arene)M(CO)3, (M = Cr, Mo, or W). Previously CO-loss was thought to be the dominant photoprocess. This thesis attempts to investigate alternative photoprocesses to CO-loss showing a direct link between the ground state electronic configurations of these systems and their photochemistry. Chapter 1 provides a general introduction to the history of organometallic chemistry. A brief description of bonding in the complexes of interest is given along with descriptions of any techniques either employed in the research or of significance to the literature survey. The bulk of this chapter deals with a literature survey of the theoretical descriptions of the electronic structure of (ri6-arene)M(CO)3 (M = Cr, Mo, or W) and [(r|6-arene)2M] (M = Cr) complexes. Chapter 2 begins with a review of the photochemistry of (t]6- arene)M(CO)3 complexes (M = Cr, Mo, or W) The quantum yield for photoinduced CO-loss in (ri6-mesitylene)Mo(CO)3 was measured at a variety of wavelengths and found to increase with decreasing wavelengths of irradiation. The variations in the electronic transitions for (ri6-mesitylene)M(CO)3, on changing the metal centre from Cr, Mo, and W were investigated using a peak fit programme. An emission spectrum of (r|6- mesitylene)W(CO)3 at 77 K is presented. This further confirms the assignments derived from the UV/vis analysis. The photochemistry of (r|6-allylbenzene)Cr(CO)3 was examined at low temperature by I.R. spectroscopy in an attempt to “trap” any ring-slip intermediate. In chapter 3 studies into the photochemistry of [(r|6-arene)2Cr]"T are detailed. Deligation of the arene rings resulted upon irradiation. Both steady state photolysis and laser flash photolysis was employed to detect and identify the intermediates of the photochemical reactions. Results suggest that the intermediates involved in aqueous solution differed from those in acetonitrile solutions. The results of investigations into the photochemistry of the bimetallic complexes [(r|6-c/'s and ¿ra«s-l,2 -diphenylethene)(Cr(CO)3)2] are presented in Chapter 4. These complexes contain low energy MLCT transitions. In the cis complex low energy irradiation resulted in cis to transisomerization while higher energy irradiation resulted in CO-loss. The molecular structural details of [(vf-trans-\,2-diphenylethene)(Cr(CO)3)2] are also included. Finally experimental details on the syntheses and techniques used during the research are given.