Synthesis, structure and formation pathways of new Fe–S complexes containing [Fe2S2]-units in different valences, [Fe2S2(CO)4(PPh3)2], [Fe3S2(CO)6(PPh3)3] and [Fe4S2(CO)10]2− and the origin of the [Fe2S2]-unit in metal–[Fe2S2(CO)6] complexes

Novel Fe–S cluster complexes, [Fe2S2(CO)4(PPh3)2] (1), [Fe3S2(CO)6(PPh3)3] (2) and [Ph4P]2[Fe4S2(CO)10] (3) have been synthesized by the reaction of LiEt3BH with [Fe2S2(CO)6] in the presence of CuCl–PPh3, AgNO3–PPh3 and CuClO3–MeCN, respectively.Structure determination indicated that 1, 2 and 3, respectively, possessed [Fe2S2]0 core with [Fe2S2]0-unit, [Fe3S2]0 with [Fe2S2]2− and [Fe4S2]2− core with [Fe2S2]4− unit, which implied that [Fe2S2(CO)6]2−, as a starting material, underwent a disproportionation in the synthetic reaction.Investigating the structure and synthetic reaction, an origin of the different valence[Fe2S2]-units and formation pathways of those clusters via disproportionation of the [Fe2S2(CO)6]2− following by ‘Unit Construction‘ were proposed and discussed.