Pincer-type Metal Complexes Constructed By The Benzimidazole Derivatives, Synthesis And Structural Characterization

A number of pincer type ligands, benzoimidazole derivatives, have been prepared and their structures were characterized by ¹H NMR spectroscopy. The reactions of these ligands with transition metals such as Pt, Pd, and Cu were studied. Pincer complexes of copper were isolated and characterized by X-ray diffraction analysis.Benzoimidazole derivatives were prepared by the dehydration reactions of organic acids with 1,2-diaminobenzene under acidic conditions at elevated temperature. The effect of solvents such as hydrochloric and polysyrup phosphoric acid were tested. A number of benzoimidazole derivatives L₁-L₆ were obtained in high yields, which are poorly soluble in common organic solvents. N-alkylation of these ligands were performed and L7-L12 were aforded. All these pincer compounds were identified by IR and ¹H NMR spectroscopies, and the structure of L₁₀ was anlyzed by X-ray diffraction. It was found that the platinum complexes of benzoimidazole ligands are vapochromic, which exhibit different colors in water, ethanol, dichloromethane, THF etc.Treatment of N-alkylated ligands L₇-L₁₂ with K₂PtCl₄, PdCl₂, Pd(cod)Cl₂, Pd(OAc)₂, and Cu(NO₃)₂.3H₂O gave pincer complexes 1-10. It was found that the platinum complexes of benzoimidazole ligands are vapochromic, which exhibitdifferent colors in water, ethanol, dichloromethane, THF etc. Reactions of benzoimidazole ligands with copper nitrate afforded mono-, dinuclear and and one-dimensional coordination polymer. X-ray diffraction analysis showed that the coordination polymer displays infinite zigzag chain structure. These complexes are potentially useful catalysts for some organic transformations or precursors as new functional materials.