New insight into the complexity of the reaction of the prominent catalyst RuC1(2)(PPh3)(3) with carbon disulfide has been obtained from a combination of X-ray diffraction and 31P NMR studies. The red-violet compound originally formulated as a cationic ir-CS, complex, [RuCl(ir-CS2)(PPh3)(3)]Cl, has been identified as a neutral molecule, RuC1(2)(S2CPPh3)(PPh3)(2), which contains the unstable zwitterion S2CPPh3. In the absence of RuC1(2)(PPh3)(3), there is no sign of a reaction between triphenylphosphine and carbon disulfide, although more basic trialk-ylphosphines form red adducts, S2CPR3. Despite the presence of an unstable ligand, RuC1(2)(S2CPPh3)(PPh3)(2) is remarkably stable. It survives melting at 173-174 C intact, is stable to air, and undergoes reversible electrochemical oxidation to form a monocation. When the reaction of RuC12(PPh3)(3) with carbon disulfide is conducted in the presence of methanol, crystals of orange [RuCl(S2CPPh3)(CS)(PPh3)21C1.2Me0H and yellow RuC1(2)(CS)(Me0H)(PP113)(2) also form. 31P NMR studies indicate that the unsymmetrical dinudear complex (SC)(Ph3P)(2)Ru(y-C1)(3)Ru(PPh3),C1 is the initial product of the reaction of RuC1(2)(PPh3)(3) with carbon disulfide. A path connecting the isolated products is presented.