Treatment of la and 1b with phenylacetylene, 1,4-diethynylbenzene, and ethynylferrocene affords addition complexes, (p-cymene)Ru(mu-E-2)Ru(S2C2B10H10)(2)(R1C=CR2), (R-1 = Ph (H), R-2 = H (Ph), 2a, 2b, 3a, 3b; R-1 = -Ph-C equivalent to CH (H), R-2 = H (-Ph-C equivalent to CH), 4a, 4b, 5a, 5b; R-1 = Fc (H), R-2 = H (Fc), 6a, 6b, 7a, 7b). Alkyne addition occurs at sulfur atoms of two different chelating 1,2-dicarba-closo-dodecaborane-1,2-dithiolate ligands that leads to a change of 16e Ru(IV) in la and 1b to 18e Ru(II) in 2a-7a and 2b-7b, respectively. Moreover, the reaction of la with ethynylferrocene produces an unprecedented tetranuclear mixed-valent Ru(IV)Ru(II)(3)S-12 cluster (8a) consisting of two la and one ethynylferrocene through the cleavage and generation of Ru-S, S-S, and C-S bonds. The complexes were characterized by IR, MS, and NMR spectroscopy and microanalysis. X-ray structural analyses were performed on 1b, 2a, 3b, 5a, 5b, 7b, and 8a.