Synthesis, characterization and electronic absorption spectra of new mononuclear cyclopalladated benzo[h]quinolinate complexes containing phosphorus ylides

The chemistry of Pd(II) complexes containing cyclometalated ligands has attracted great interest in recent years due to their applications in different areas [1-3]. A series of mononuclear cyclopalladated benzo[h]quinolinate complexes with bidentate phosphine ligands, namely, [Pd(bzq)((Ph2PCH2PPh2C(H)C(O)PhR)]ClO4 (R = Cl (1), Br (2) NO2 (3) OCH3 (4), were synthesized. The reactions of [Pd(bzq)(μ-Cl)]2 with bidentate phosphorus ylide (1:2 molar ratio) in presence of NaClO4 led to the splitting of the chloride bridge and obtained the mononuclear complexes that benzoquinolinate and phosphours ligand are bonded to the Pd atom giving two five membered rings. These complexes were fully characterized by elemental analysis, IR, 1H, 31P, and 13C NMR. The spectroscopic data revealed that the phosphorus ylide is coordinated to palladium via the phosphine group (PPh2) and methene group (CH). These analyses being consistent with a 1:1:1 stoichiometry bzq/ylide/Pd(II) for compounds 1 through 4. In addition, the UV-vis absorption spectra of complexes were recorded in dichloromethane solvent at 298 K. All of the complexes exhibit absorption bands at high energy due to the intraligand transitions (π→π*) and absorptions at lower energy which are attributed to MLCT transition (π→π*). Also the absorption spectra of complex 3 were recorded in several solvents such as acetonitrile and acetone.