The cluster HRu 3 (CO) 9 [NS(O)MePh] (1) reacts with two equivalents of MeC≡CMe in tetrahydrofuran at 60 o C to give the dienonyl derivative Ru 3 (CO) 7 [NS(O)MePh](HCMeCMeCMeCMeCO) (2), along with an isomer mixture of Ru 3 (CO) 8 [NS(O)MePh](HCMeCMe) (3). At 100 o C, the same reaction gives rise to the formation of the diendiyl cluster Ru 3 (CO) 8 (CMeCMeCMeCMe) (4). The single-crystal structure analyses reveal for 2 a closed Ru 3 skeleton and for 4 an open Ru 3 framework.