Reaction of dialkylcarbodi-imides with Fe(CO)5 affords novel compounds having the general formula C(NR)3Fe2-(CO)6(R = Pri, C6H11). Acid hydrolysis indicates that the trialkylguanidine moiety is present in the complex, and is attached through nitrogen atoms to a Fe2(CO)6 group, which contains an Fe–Fe bond. I.r., n.m.r., and mass spectral data are consistent with the formulation of the ligand as a dehydrotrialkylguanidine. A possible mechanism for formation of the product is proposed.