Binuclear and polymeric Hg(II) complexes of an ambidentate phosphorus ylide: Synthesis,crystal structure,antibacterial activity,and theoretical studies

The new α-keto-stabilized phosphorus ylide Ph₃PCHC(O)PhCN ( Y ) was synthesized by addition of triphenylphosphine to 2-bromo-4′-cyanoacetophenone, followed by treatment with NaOH 10%. Reaction of ligand ( Y ) with methanolic solution of mercury(II) halides under mild conditions yielded the binuclear complexes [Y·HgX₂]₂ [X=Cl ( 1 ), Br ( 2 ), I ( 3 )]. The new organic/inorganic composite polymer [Hg(NO₃)₂(Y)]_n ( 4 ) was synthesized by the reaction of mercury(II) nitrate with the phosphorus ylide Y . Compounds synthesized were characterized by Fourier-transform infrared, ¹H, ³¹P, and ¹³C nuclear magnetic resonance spectroscopic methods, which confirmed the coordination of ylide to the metal center through the ylidic carbon atom. Single-crystal X-ray structures of phosphorus ylide Y and polymeric complex 4 were also determined and the crystallographic data of complex 4 showed that the title complex has an infinite one-dimensional structure. Furthermore, the electronic and molecular structures of complexes 1 – 3 were investigated at the BP86/def2-SVP level of theory, indicating an increasing trend for C→M bond lengths: Hg₂I₂ > Hg₂Br₂ > Hg₂Cl₂ in [Y→HgX₂]₂ (X = Cl, Br, I) complexes. In addition, the antibacterial activity of ligand Y and all complexes using the agar disc diffusion method was examined against both selected gram-positive and gram-negative bacteria. Results indicated that the ligand Y and complexes 1 and 4 show good antibacterial effect against gram-positive bacteria tested; besides, the inhibition zones of complexes were significantly larger than those of chloramphenicol as standard.