The photochemistry of some d6 metal carbonyl complexes is investigated. In particular, the effect of the substitution of a carbon monoxide ligand by a tnphenylphosphine ligand on the reactivity of the intermediates formed on photolysis of these complexes is examined. The manganese complexes (775-C5H4CH3)Mn(CO)3 and (tj5- C5H4CH3)Mn(CO)2PPh3 are investigated by laser flash photolysis (X = 355nm). The laser flash photolysis ( \ = 266nm, 355nm) of the Group VI M(CO)5PPh3 (M = Cr, Mo or W) complexes is also îeported. The crystal structures of the (T/5-C5H4CH3)Mn(CO)2L (L = pyridine, cvs-cyclooctene) complexes are presented and examined to see the effects of a good a donating ligand and a good n accepting ligand on the (775-C5H4CH3)Mn(CO)2 unit. A program wntten in GWBASIC for transient capture and analysis is described.