Synthesis and Crystal Structures of an Unexpected Tetranuclear Zinc(II) Complex and a Benzoquinone Compound Derived from ZnII‐ and CdII‐Promoted Reactivity of Schiff Base Ligands |
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| Authors: | Bin Yu Yin‐Xia Sun Cheng‐Juan Yang Jian‐Qiang Guo Jing Li |
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| Affiliation: | School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou, P. R. China |
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| Abstract: | An unexpected polyhydroxyl‐bridged tetranuclear ZnII complex and a benzoquinone compound derived from metal‐ion promoted reactivity of Schiff base ligands were synthesized and characterized. The reaction of zinc(II) acetate dihydrate with oxime‐type Schiff base ligand HL1 HL1 = 1‐(3‐((3,5‐dibromosalicylaldehyde)amino)phenyl)ethan‐1‐one O‐benzyl oxime] in methanol, acetone, and acetonitrile resulted in the chemoselective cleavage of the C=N bond of the Schiff base HL1, and then the further addition of acetone to two salicylaldehyde molecules derived from cleavage of the C=N bond in situ α,α double aldol reaction promoted by ZnII ions. The newly formed ligands H4L2 coordinate to four ZnII ions forming a defect‐dicubane core structure ZnII4(H2L2)2(μ3‐OCH3)2(μ‐OCH3)2(CH3OH)2] ( 1 ) bridged exclusively by oxygen‐based ligands. The similar ligand HL3 HL3 = 1‐(3‐((3,5‐dichlorosalicylaldehyde)amino)phenyl)ethan‐1‐one O‐benzyl oxime)] was employed to react with CdII acetate dihydrate under the same reaction conditions. No aldol addition occurred but a unexpected benzoquinone compound 2,5‐bis(((3‐(1‐((benzyloxy)imino)ethyl)phenyl)imino)methyl)‐1,4‐benzoquinone ( 2 ) formed. The results provided interesting insights into one‐pot routes involving in situ reactions act as a strategy for obtaining a variety of polymeric/polynuclear complexes which are inconvenient to obtain from directly presynthesizing the ligands. |
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| Keywords: | Metal‐ion promoted Double aldol addition Schiff bases Zinc Crystal structure |
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