In this thesis, we reported a novel catalyst system for immobolized palladium metal-containing magnetic nanoparticles core (ImmPd(0)-M) for Heck and Suzuki coupling, carbonylation of aryl halides and synthesis of benzimidazole derivatives. The catalyst was characterized by TEM, SEM, XRD, EDX, FT-IR, TGA and VSM. The ImmPd(0)-M is found as an exceptionally mild and versatile catalyst for Heck and Suzuki reactions of aryl iodides and bromides at room temperature. The catalyst was simply reused by an external magnet from the reaction mixture and recycled several times. The results showed that the catalyst was very active and stable. Moreover, these reactions was carried out in water as a green and environmentally acceptable solvent. This phosphine-free catalyst also demonstrated good activity for carbonylation reactions, containing alkoxycarbonylation, aminocarbonylation, carbonylative Suzuki and carbonylative hiyama reactions. Various substituted aryl iodides tolerated the reaction conditions and a wide variety of amides, esters and ketones were synthesized in the presence of Mo(CO) 6 as a carbon monoxide reagent.. The effects of solvent, base and temperature were studied in all reactions. The developed catalytic system avoids the use of phosphine ligands and can be reused for up to eight consecutive cycles. Finally, this catalytic system was used for the synthesis of benzimidazoles starting from o-phenylenediamines and amines. It is possible to use a tertiary, a secondary, and even a primary amine as the substrate for a palladium-mediated process to get 2-substituted benzimidazoles. Primary amines are the most suitable reagents for the atom economy of the overall process that resulted to be general as several different substituted benzimidazoles were obtained in good yield.