Synthesis of an adj-Dicarbaporphyrin and the Formation of an Unprecedented Tripalladium Sandwich Complex

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• 作者：Deyaa I. AbuSalim ; Gregory M. Ferrence ; Timothy D. Lash
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：May 7, 2014
• 年：2014
• 卷：136
• 期：18
• 页码：6763-6772
• 全文大小：744K
• 年卷期：v.136,no.18(May 7, 2014)
• ISSN：1520-5126

文摘

An adj-dicarbaporphyrin was prepared by carrying out a base-catalyzed MacDonald reaction between bis(3-indenyl)methane and a dipyrrylmethane dialdehyde. The porphyrinoid system exhibited highly diatropic characteristics, and the proton NMR spectrum gave resonances at 鈭?.74 and 鈭?.24 ppm for the internal NH and CH protons, respectively. The UV鈥搗is spectrum was also porphyrin-like, giving a Soret band at 455 nm and a series of Q bands at longer wavelengths. Addition of trifluoroacetic acid gave a C-protonated monocation, and at higher acid concentrations a dicationic species was observed. Addition of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) afforded a monodeprotonated porphyrinoid anion. All of these species retained highly diatropic characteristics. Density functional theory calculations showed that a nonplanar tautomer with four internal hydrogens was favored, in agreement with the spectroscopic data. Nucleus-independent chemical shift calculations also confirmed the aromatic characteristics of the free-base, cationic, and anionic structures. The dicarbaporphyrin reacted with palladium(II) acetate in refluxing acetonitrile to give an unusual tripalladium sandwich complex consisting of two dianionic palladium(II) dicarbaporphyrin units surrounding a palladium(IV) cation with unique 畏⁵ interactions involving meso-carbon atoms.