The application of acyclic (diene)iron complexes and (pentadienyl)iron cations in organic synthesis has steadily increased over the past 20 years. This is due to their ease of preparation, their stability toward a wide variety of reaction conditions, the manifold method for removal of the Fe(CO)3 group, and the low cost of iron carbonyls. The (tricarbonyl)iron adjunct may serve in three capacities: i) as a protecting group for conjugated dienes, ii) to direct the formation of chiral centers adjacent to the complexed dient, and iii) to stabilize the formation of positive charge adjacent ot the complexed diene (i.e. pentadienyl cations). Specific examples of these attributes will be presented in this review. One of the advantages of stoichiometric organometallic reagents is the ability to repeatedly utilize the same metal center to control a number of different bond forming reactions. Six examples will be presented which demonstrate this potential for acyclic (diene)iron complexes and (pentadienyl) iron cations.