By the reaction of Co2(CO)8 with 2-thiohydantoins S-CNHC(O)C(R1) (R2)NC(O)R3(HL), a new cluster with formula Co3(CO)7 (μ3-S) (μ3, η2-S CNC(O)C(CH3)2N C(O)CH3 hasbeen prepared. The cluster has been characterized by elemental analysis, IR, 1H NMR and MS spectroscopy.The crystal structure of the cluster has been determined by X-ray single crystal diffraction method.The crystal of the cluster is triclinic, belonging to space group P1 and the cell parameters are as follows: a=8.456 (3), b=11.534(3), c= l1.990(4)A, α=107.36(3), β=108.44(5), γ=90.,18(3)°. Thestructural analysis shows that this molecule contains a tetrahedral cluster framword Co3S and2-thiohydantoin as bridging ligands links up with two cobalt atoms of the framwork by S- andN-atom thus -a five member ring of Co2 NCS has been formed.