C-H Bond Activation of Bisimines by Palladium （II） and Platinum （II）. Synthesis, Characterization of Bis（imino）aryl-palladium （II） Pincer Complexes and Their Application in Carbon-Carbon Cross Coupling Reactions

The reactions of a variety of 4,6-dimethyl-1,3-bis(imino)benzenes 2a-g derived from 4,6-dimethylisophthalaldehyde and anilines or benzylamine with palladium(II)acetate in anhydrous acetic acid under nitrogen were investigated.Experiment results demonstrate that cyclopalladations in such condition are applicable not only to the present system under study but also to the 5-substituted bis(imino)benzenes 6,7.The molecular structure of 3b was further confirmed by X-Ray single-crystal diffraction.3b Crystallizes in orthorhombic,space group P2(1)2(1)2(1)with a=0.734 53(8),b=1.683 8(3),c=1.691 7(2)nm,α=β=γ=90°.Treatment of 2b with K2PtCl4in anhydrous acetic acid affords the corresponding NCN-platinum pincer.Carbon-carbon cross coupling reactions catalyzed with 3b were investigated.These palladium complexes have been proved to be high effective catalysts for Suzuki coupling reaction.