The aim of this work was to determine the photochemical properties of a number of compounds of the general type (r|x-arene)M(CO)3 (M=Cr, Mn, X = 5,6). A range of techniques were used including ultraviolet/visible flash photolysis, time resolved infrared spectroscopy and matrix isolation. The first chapter contains a literature survey of the group 6 and 7 metal carbonyl complexes, also presented is a brief description of the role of transition metal complexes in some important industrial processes. In addition, the metal carbonyl bond and the metal arene bond are described, while the nature of the absorption spectra of group 6 and 7 metal carbonyls are discussed, as are their known photochemical and thermal properties. The second chapter describes the photochemistry of functionalised (r|6-C6H5X)M(CO)3 Complexes ( X = OCH3, NH2, CO2CH3 or C(O)H). The nature of the functionality on the arene ring has been shown to affect the photochemical properties of these complexes. The relative importance of CO loss versus arene loss is measured and these observations are explained in terms of electronic character of the arene substituent. The third and fourth chapters deal with the photochemistry of a series of compounds which are used to model the hydrodesulphurisation reaction, namely (ri5-thiophene)Cr(CO)3, (r]6-benzothiophene)Cr(CO)3, (r|6-dibenzothiophene)Cr(CO)3 and (r|5-selenophene)Cr(CO)3. Both steady state photolysis and time-resolved techniques were used to investigate the photochemistry of these complexes. In addition to CO loss, evidence of a hapticity change from r|5 to r|4 is observed for (ri5-thiophene)Cr(CO)3 and (r|5-selenophene)Cr(CO)3 under photochemical conditions. This research was also extended to group 7 metal carbonyls. The fifth chapter deals with the photochemistry of (r]5-pyrrollyl)Mn(CO)3. While CO loss was observed as the dominant photoprocess, evidence for a ring-slip process was also obtained. The sixth chapter details the different synthetic procedures used, as well as the experimental techniques of ultraviolet/visible flash photolysis, time resolved infrared spectroscopy and matrix isolation techniques.