Reaction of Mo2Ir3(μ-CO)3(CO)6(η5-C5H5)2(η5-C5Me5) with Ir(CO)2(η5-C5Me4H) afforded the four-valence-electron-deficient butterfly cluster Ir4(CO)6(η5-C5Me4H)2; its stability has been rationalized with the aid of density functional theory calculations, which suggest that significant additional intracluster bonding alleviates the formal electron deficiency. Reaction of MoIr4(CO)10(η5-C5H5)(η5-C5Me5) with [N(PPh3)2][Ir(CO)4] afforded the capped octahedral cluster Ir7(μ3-CO)3(CO)12(η5-C5Me5), which possesses three semi-face-capping CO ligands. These outcomes demonstrate that heterometallic clusters may serve as a potential source of new homometallic clusters following appropriate M–M′ cleavage.