In this thesis, phosphorus ylides [PhY] and [NO 2 Y] have been synthesized through the formation of phosphonium salt and dihydrogenation, followed by the reaction of Pd(OAc) 2 and the orthopalladated dinuclear complexes [Pd(?-R)(NO 2 Y)] 2 R= Cl, Br and I have been prepared. The reaction of dinuclear complexes and monodentate ligands [L =4-methyl prydine (4-MePy), 2,4,6-symcollidine giving the stabilized mononuclear orthopalladated complexes [Pd(Br)(NO 2 Y)(4-MePy)], [Pd(Br)(NO 2 Y)(PPh 3 )], [Pd(Br)(NO 2 Y)(Me 3 Py)], [Pd(Cl)(NO 2 Y)(PPh 3 )] and [Pd(Cl)(Me 3 Py)(NO 2 Y)] in endo position. The complexes were chracterized by FT-IR, NMR, UV-Vis and X-ray diffraction study of [Pd(4-MePy)(NO 2 Y)(Br)], [Pd(Br)(NO 2 Y)].The ?(CO) band which is sensitive to complexation occurs from 1507 and 1521 cm -1 in the parent ylides. These bands appear at lower energies compared to that found in the phosphonium salts, due to the charge delocalization present in such compounds. Coordination of ylide through the carbon atom causes an increase in the ?(CO) band. The FT-IR spectra of all complexes show a strong absorption in the range of 1621-1637 cm -1 , which have been shifted to higher frequency with respect to the parent ylides, meaning that the ylides are C-bonded to the palladium center. The ?(P-C) band frequencies occur at 881 and 860 cm -1 in the parent ylides [PhY] and [NO 2 Y], respectively and are shifted to lower frequencies for the complexes (852-854), suggesting some removal of the electron density of the P-C bonds. The 1 H NMR signals for the PCH group of complexes are shifted downfield compared to that of the free ylides, as a consequence of the inductive effect of the metal center. In the 1 H NMR spectra for dinuclear complexes, the signals due to the methinic proton were broad (minor) or broad doublets (major). The presence of two lines of different intensity on each spectrum can be originated from the presence of two diasteroisomers (RR/SS and RS/SR), as a result of the C-bonding of the ylide and the dinuclear nature of ([Pd(?-R)(NO 2 Y)] 2 (R=Cl, Br, I). In the 31 P [ 1 H] NMR spectra of all complexes, the presence of one signal group, confirm a single isomer for each complexes. Single crystals of [Pd(Br)(4-MePy)(NO 2 Y)] and [Pd(Br)(Me 3 Py)(NO 2 Y)] suitable for X-ray crystallography, were obtained. Although the orthometallated ligand is remarkably warped, the environment around the Pd is planar. In the last section, these complexes are used in Suzuki coupling.