Synthesis, characterization, and theoretical studies on ylidic complexes of mercury(II) as antioxidant agents

Abstract

Herein we describe the synthesis of a library of new mercury complexes, including some dimers and polymeric species. Initially, a phosphonium salt, [PPh3CH2C(O)C6H4–m-OCH3]Br (S), was synthesized from triphenylphosphine (PPh3) and BrCH2C(O)C6H4-m-OCH3 in acetone. We then reacted this phosphonium salt with an appropriate base to acquire a new phosphorus ylide monodentate, PPh3=C(H)C(O)C6H4-m-OCH3 (Y). Finally, we treated the synthesized ligand with mercury halides in dry CH3OH to form C-coordinated complexes of the form [HgX(PPh3C(H)C(O)C6H4-m-OCH3) (μ-X)]2 [X = Cl (1), Br (2), I (3)], [(PPh3=C(H)C(O)C6H4-m-OCH3)Hg(NO3)2]n (4). We characterized these compounds using CHN analysis, FT-IR, NMR (1H, 13C and 31P) and density functional theory. We elucidated the structure of 2 by single-crystal X-ray diffraction. The results establish that 1, 2 and 3 have dimeric structures, while a polymeric structure is suggested for 4. The antioxidant activity of all compounds in DMSO was assessed using a DPPH free radical scavenging method. Also, the nature of metal-ligand (C→Hg) bonding in 1, 2 and 3 have been investigated using natural bond orbital (NBO) and energy-decomposition analyses (EDA).