The reaction of Na[HRu3(CO)11] (2) with SbPh2Cl in dry tetrahydrofuran (THF) afforded the cluster Ru3(CO)10(μ-H)(μ-SbPh2) (3); in dry dichloromethane (DCM), the six-membered ring Ru6(CO)20(μ-H)2(μ-SbPh2)2 (4) was obtained instead. The trimethylamine N-oxide (TMNO) activated reaction of Ru3(CO)12 (1) with distibine Sb2Ph4 produced Ru3(CO)10(μ-SbPh2)2 (6) through an Sb-Sb bond oxidative addition. Cluster 6 is fluxional through Ru-Ru bond isomerization. In contrast, its group 15 monosubstituted derivatives Ru3(CO)9(μ-SbPh2)2(L) (7, L = phosphane, arsine or stibine) or the disubstituted derivatives Ru3(CO)8(μ-SbPh2)2(L)2 (8) did not exhibit such fluxionality. Instead, isomerization through a turnstile mechanism involving the group 15 ligand occurred. The treatment of 6 with SbPh2Cl afforded the fused-ring clusters Ru3(CO)9(μ-SbPh2)3(Cl) (9) and Ru3(CO)8(μ-SbPh2)3(Cl)(SbPh2CH2Cl) (10). A series of ruthenium-antimony carbonyl clusters are prepared by the oxidative addition of Sb-Cl or Sb-Sb bonds to lightly stabilized ruthenium carbonyl clusters. Their solid- and solution-state structures are studied in detail by X-ray crystallography and variable-temperature multinuclear NMR experiments, respectively. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.