Treatment of Cp*2Os2Br4 with 3-bromo-2-methylpropene or 1,3-cyclooctadiene affords the 2-methylpropenyl and cyclooctenyl products Cp*Os(η3-C4H7)Br2 and Cp*Os(η3-C8H13)Br2, respectively. The monoalkyl complexes Cp*Os(η3-C4H7)MeBr and Cp*Os(η3-C4H7)(CH2SiMe3)Br can be generated by treating Cp*Os(η3-C4H7)Br2 with MgMe2 or LiCH2SiMe3. The dimethyl complex Cp*Os(η3-C4H7)Me2 can be synthesized from Cp*Os(η3-C4H7)Br2 by addition of methyllithium. In contrast, addition of ethyllithium to Cp*Os(η3-C4H7)Br2 yields the ethylene complex Cp*Os(η3-C4H7)(η2-C2H4) and a small amount of Cp*Os(η3-C4H7)H2. The latter dihydride can be synthesized in better yield by treating Cp*Os(η3-C4H7)Br2 with LiAlH4. When the dimethyl complex Cp*Os(η3-C4H7)Me2 is protonated with HBF4 in the presence of H2O, the aqua complex Cp*Os(η3-C4H7)Me(H2O)BF4 is formed.