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Reaction of (Ru2(CO)6(μ-PFu2)(μ- 1 , 2 -Fu)) (Fu = furyl) 1 with tri(2-furyl)phosphine under thermal conditions produces simple mono- and disubstitution products (Ru2(CO)5(PFu3)(μ-PFu2)(μ- 1 , 2 -Fu)) 2a and (Ru2(CO)4(PFu3)2(μ- PFu2)(μ- 1 , 2 -Fu)) 2b. Both complexes were fully characterized by spectroscopic and analytical methods and the molecu- lar structures of 2a and 2b were established by X-ray crystallography. The Ru Ru edge bridged by the μ- 1 , 2 -bound PFu2 fragment remains intact after the substitution reaction. The product yields of both complexes depend on the stoichiometry of the reactants. All of these new diruthenium complexes are electron precise with 34 cluster valence elec- trons. tion metals in low oxidation states (4). The pioneering work by Farina and co-workers showed the use of PFu3- derived palladium catalysts to be highly advantageous in the Stille cross-coupling reaction with significant rate ac- celerations being observed over traditional PPh3-based catalysts, presumably by virtue of its low electron-donating ability toward Pd(II) center (5). Since then, numerous re- searchers have sought to evaluate the performance of PFu3 in a wide variety of metal-catalyzed processes for the preparation of small molecules, complex natural products as well as polymers (3). In many cases, Stille coupling with the PFu3 ligand allows for milder reaction conditions and hence the attenuation of unwanted side reactions. How- ever, accurate prediction of whether this poor  -donating PFu3 ligand will lead to beneficial effects for a given proc- ess still remains elusive.