Transition metal carbonyls (Ir4(CO)12, Os3(CO)12 and M(CO)3 (PPh3)2 M=Ru or Os) have been reacted with XeF2, and Os3(CO)12 with fluorine gas. The products have been fully characterised by NMR spectroscopy, 19F, 13C, 13C{19F} and 31P where appropriate. For the reactions between Ir4(CO)12 and Os3(CO)12, the presence of hydrogen fluoride was observed to be critical, to the subsequent fluorinations, the first stage of the reaction being protonation of the carbonyl clusters. The resulting transition metal carbonyl fluorides are observed to be reactive towards tertiary phosphines, resulting in the formation of carbonyl phosphine fluoro-complexes. For the reactions between the five coordinate species M(CO)3 (PPh3)2 (M=Ru or Os) and XeF2, oxidative addition not only results in the formation of a M-F bond, but also produces the novel fluoroacyl ligand (-COF). These reactions were followed by variable temperature NMR spectroscopy. This enabled the elucidation of the overall mechanism for the reaction, which ultimately afforded the respective MF2(CO)2(PPh3)2 complexes.