Cyclopentadienyliron dicarbonyl dimer is an organometallic compound with the formula (η5-C₅H₅)₂Fe₂(CO)₄, also abbreviated Cp₂Fe₂(CO)₄. It is called Fp₂ or "fip dimer." It is a dark reddish-purple crystalline solid, which is readily soluble in moderately polar organic solvents such as chloroform and pyridine, but less soluble in carbon tetrachloride and carbon disulfide. Cp₂Fe₂(CO)₄ is insoluble in but stable toward water.