Synthesis of bis-2H and 4H-chalcogenapyrans and benzochalcogenapyrans via Pd⁰ catalyzed dimerization of Fischer type carbene complexes: redox properties and electronic structure of these new extended electron rich molecules

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• 作者：Nadè ; ge Faux ; Franç ; oise Robin-Le Guen ; Pascal Le Poul ; Bertr ; Caro ; Nicolas Le Poul ; Yves Le Mest ; Stephen J. Green ; Sé ; bastien Le Roux ; Samia Kahlal ; Jean-Yves Saillard
• 关键词：Fischer type carbene complexes ; Bispyrans ; Cyclic voltammetry ; DFT calculations
• 刊名：Tetrahedron
• 出版年：2007
• 出版时间：23 July 2007
• 年：2007
• 卷：63
• 期：30
• 页码：7142-7153
• 全文大小：755 K

文摘

Extended electron rich bis-chalcogenapyrans and bis-benzochalcogenapyrans have been synthesized by Pd⁰ catalyzed dimerization of α- and γ-methylene chalcogenapyran and benzochalcogenapyran Fischer type carbene complexes. Voltammetric studies performed on these molecules show a single two-electron wave around 0 V versus SCE, which is ascribed to the oxidation of the neutral form in radical and dipyrylium cations. DFT calculations show that the oxidation leads to a rotating movement around the central C–C bond and suggest that the solvent plays a major role in the observation of the two one-electron systems. Furthermore, according to the structure, these molecules are likely to be reduced at very low potential (E=−1.5 V vs SCE) via a two-electron transfer reaction.