The reaction between the cluster dianion [Fe3(μ3-Y)(CO)9]2− (1) (Y=Se (a), Te (b)) and MesSbBr2 leads to the formation of [Fe3(μ3-Y)(μ3-SbMes)(CO)9] (2a,b) (Mes=2,4,6-Me3C6H2). The molecular structures of both compounds were established by single crystal X-ray diffraction and reveals nido cluster cores containing square pyramidal FeSbFeY units capped by a third Fe carbonyl fragment as an apical vertex. The novel compound [Fe3(μ3,η2:η1-SeSbMes)(μ3-SbMes)(CO)10] (3) was obtained by a similar reaction via slightly modified reaction conditions. This molecule contains a Fe(CO)4 and a Fe2(CO)6 fragment, respectively, which are connected by a μ3-SbMes and a novel μ3,η2:η1-SeSbMes ligand.