Abstract: The reaction of Fe₃(CO)₁₂with 2, 4-dithiohydantoins SCNHC(R₁)(R₂)C(S)NH(SL) yields the known Fe₃(CO)₉(u₃-S)₂and the five new open triangular iron carbonyl clus ters Fe₃(CO)₈(u₃-S)₂(L)1-5. It was found that the coordinated ligands in the clusters 1-5 besides eight terminal COligands are two sulfito Satoms and a heterocyclic carbene Lwhich was formed from the cleavage of the ligand precursor SL. The formulas and structures of these clusters were characterized by elementary analysis, IR, ¹HNMR and MS techniques and the molecular structure of 3 was determined by X-ray diffraction analysis. The sp²bond ing character of the carbon (carbene) atom of fragmental 2,4-dithiohydantoin: CNHC(CH₃)₂C(S)NH shown clearly in 3 and the C_carh.-Fe bond length of 0. 1898 nm cor responds to other iron stabilized carbenes. This carbene ligand displaced a terminal axial CO of the basal Fe(1) atom and locates in a vertical position to the Fe (1)S(1)Fe(3)S(2) distort ed basal plane. The geometry of Fe₃(CO)₉(u₃-S)₂has been maintained in 3, but some of Fe-S and Fe-Fe bond lengths have been changed.

Key words: Iron carbonyl cluster, Metal carbene, Fragments of 2,4-dithiohydantoin