The reaction of [(cymene)RuCl2](2) (1) with PCY3 was investigated using different stoichiometries and reaction conditions. Whereas a mixture of complex 1 and 2 equiv of PCy3 in methanol gave the known adduct [(cymene)Rucl(2)(PCy3)] (3) along with the phosphonium salt [PCy3(CH2OH)]Cl (4). prolonged heating of 1 and 4 equiv of PCy3 in methanol under argon resulted in the formation of complex [RuHCl(CO)(PCy3)(2)] (5). Dinuclear, chloro-bridged complexes were generated when 1 was reacted with only 1 equiv of PCy3]. In a mixture of THF and allyl alcohol. the carbonyl complex [(cymenc) Ru-(mu-cl)(3)Rucl(CO)(PCy3)](6) was formed. In dioxane, however, intramolecular C-H activation of the PCy3 ligand was observed. resulting in the formation of [(Cymene)R mu-Cl)(3)RuCl{PCy2(C6H9)}] (7). When the reaction was performed under an atmosphere of H-2,H- the dihydrogen complex [(cymene)Ru-(mu-Cl)(3)RuCl(H-2)(PCy3)] (8) could be isolated. An inert trinuclear cluster of the formula [RuCl2(PCy3)](3) (10) was formed when 1 was heated with 2 equiv of PCy3 in THF. Complexes 3, 6, 7, 8, and 10 as well as the phosphorium salt 4 were characterized by single-crystal X-ray analysis.