The characterization and the photochemical investigation of a Ru-II complex (Ru(PPh3)(3)Cl-2) having phosphine ligands are reported. DFT calculations and ESR spin trapping experiments revealed for the first time that the photodecomposition of the complex is governed by a homolytic cleavage of the P (C6H5) bond generating phenyl radicals Ph-center dot which are able to initiate the free radical polymerization of acrylate monomers. The addition of a H-donor HD plays a key role in the cationic photopolymerization of epoxides: (i) the reaction efficiency is enhanced using [Ru(PPh3)(3)Cl-2]/HD and (ii) the in situ formation of Ag nanoparticles is observed in the presence of Ru(PPh3)(3)Cl-2/HD/AgSbF6 according to the following reactions: Ph-center dot/DH hydrogen abstraction yielding a D-center dot radical and oxidation of D-center dot by the silver salt.