This thesis probes the catalysis of phosphoryl transfer reactions by Fe(II), with particular emphasis on biologically relevant examples. The results of this thesis may have important implications for the origin of metabolism and the origin of phosphate in metabolism. Chapters two and three describe the phosphoryl transfer reactions of acetyl phosphate and phosphoenolpyruvate in the presence of Fe(II). The effect of various factors, including the pH, amount of Fe(II) present and temperature are investigated. Fe(II) was found to be an effective catalyst for phosphoryl transfer to inorganic phosphate. Phosphoryl transfer from either acetyl phosphate or phosphoenolpyruvate to inorganic phosphate may provide a feasible route for the prebiotic production of pyrophosphate. The hydrolysis of polyphosphates is described in chapter four. Pyrophosphate was found to be more stable with respect towards hydrolysis in the presence of Fe(II) compared to in the absence of Fe(II). Tripolyphosphate, ADP and ATP were found to be less stable with respect to hydrolysis in the presence of Fe(II). The hydrolysis of ATP in the presence of Fe(II) was found to proceed by two pathways. The major pathway involved loss of the terminal phosphate and resulted in the formation of ADP and phosphate. However, a significant amount of ATP hydrolysed by an alternative pathway that resulted in the production of AMP and pyrophosphate. The effect of Fe(II) on the hydrolysis of these compounds may have implications for the selection of ATP as the predominant source of free energy in biological systems.