The reaction of bis(dimethylphosphino)methane with Ru3(CO)12under CO pressure at 120 °C leads to the quantitative formation of the binuclear ruthenium complex Ru2(dmpm)2(CO)5. Although this complex was previously unreported, the spectroscopic data and X-ray crystallographic analysis [P1* space group, a = 10.569 (2) Å, b = 11.964 (2) Å, c = 12.232 (4) Å, a = 77.22 (2)°, β = 77.53 (3)°, γ = 75.14 (3)°, V = 1437 (1) Å3, Z= 2] show that it has a structure analogous to that found for related binucleating diphosphines. The reaction of Ru2(dmpm)2(CO)5with acids such as HBF4 occurs rapidly and leads to quantitative protonation of the metal-metal bond forming [HRu2(dmpm)2(CO)5]BF4. The reaction with diphenylacetylene occurs at 90 °C in toluene leading to Ru2(dmpm)2(CO)4(C6H5CCC6H5), which was shown to contain a σ2-bridging acetylene ligand by X-ray crystallography [P21/a space group, a = 13.140 (3) Å, b = 15.157 (4) Å, c = 16.280 (3) Å, β = 92.56 (2)°, V = 3239 (2) Å3, Z = 4]. Although the analogous product can be isolated by treating Ru2(dmpm)2(CO)5with MeO2CCCCO2Me at 70 °C, several intermediates can be observed by conducting the reaction at lower temperatures.