It is now understood that coordinatively unsaturated metal fragments bind rapidly to a solvent molecule. The role of this solvent-metal interaction in mediating reactions is investigated in this study. Chapter 1 serves as a general introduction and review of the structure, reactivity and photochemistry of these coordinatively unsaturated species and the techniques employed in order to investigate these species. The second chapter deals with the formation of solvent substituted pentacarbonyl species by flash photolysis of Cr(CO)6 in various alkane solvents. The nature of the solvent interaction with the Cr(CO>5 fragment was investigated by monitoring the displacement of the various alkane solvents by CO. The rate of reaction of the solvated species with CO was found to depend on the alkane solvent. The enthalpies of activation for all the reactions were very similar (Atf= 20 ± 4 kJmol'l), while the entropy of activation values for the aliphatic alkanes increased with increasing length of the hydrocarbon chain (AS*= -60 and -39 Jmol‘ lK‘1 for pentane and heptane respectively). In chapter 3 the rate of reaction of Cr(CO)5(S), (S = cyclohexane, toluene, THF or ethanol) with various substituted-pyridine nucleophiles is investigated using laser flash photolysis and stopped-flow techniques. Differences in the rates of reaction were attributed to the steric and electronic effects of the substituents on the nucleophiles rather than the basicity of the nucleophiles. The rates of reaction were also influenced by the nature of the solvent-metal interaction. The activation parameters associated with these reactions were also measured. In the fourth chapter the photochemistry of (r|6-C6H6)Cr(CO)3 is investigated. The solvated dicarbonyl complex is produced upon laser flash photolysis of (T|6-C6H6)Cr(CO)3 and the rate of reaction of this complex with pyridine or 4-acetylpyridine is investigated. In addition, (T|6-CgH6)Cr(CO)2(L) 0- = pyridine, 4-acetylpyridine) complexes are synthesised and the photochemistry of these complexes in the presence of excess ligand are also investigated. Irradiation of Cn6-CgH(5)Cr(CO)2(pyridine) resulted in regeneration of the pyridine complex, while two isomeric complexes in which bonding was via the oxygen atom and the nitrogen atom were obtained for the 4-acetylpyridine complex. The O-linked isomer was short-lived. The final chapter deals with all the experimental techniques encountered in the course of this work.