A Pd4Br4 macrocycle trapped by cocrystallization from a highly dynamic equilibrium of η3-cycloheptatrienide complexes

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• 作者：C. Jandl ; S. Stegbauer and A. Pö ; thig
• 关键词：cocrystal ; organometallic palladium(II) complex ; dimer ; tetramer ; low-temperature NMR ; coordination chemistry ; crystal structure ; dynamic equilibrium ; Pd4Br4 macrocycle
• 刊名：Acta Crystallographica Section C
• 出版年：2016
• 出版时间：July 2016
• 年：2016
• 卷：72
• 期：7
• 页码：509-513
• 全文大小：862K
• ISSN：1600-5759

文摘

In the coordination chemistry of palladium, dimers bridged via halides are a common motif. Higher oligomers, however, are still rare. We report the structure of an alternating eight-membered [Pd₄Br₄]⁴⁻ ring framed by cycloheptatrienide ligands, which was obtained by cocrystallization of dimers and tetramers of the complex salt bromido{η³-[3-(2,6-diisopropylphenyl)imidazolium-1-yl]cycloheptatrienido}palladium(II) tetrafluoroborate, namely bis[di-μ-bromido-bis({η³-[3-(2,6-diisopropylphenyl)imidazolium-1-yl]cycloheptatrienido}palladium(II))] cyclo-tetra-μ-bromido-tetrakis({η³-[3-(2,6-diisopropylphenyl)imidazolium-1-yl]cycloheptatrienido}palladium(II)) octakis(tetrafluoroborate) dichloromethane octasolvate, [Pd₄Br₄(C₂₂H₂₆N₂)₄][Pd₂Br₂(C₂₂H₂₆N₂)₂]₂(BF₄)₈·8CH₂Cl₂. These dimers and tetramers form a highly dynamic equilibrium in solution which was studied by low-temperature NMR spectroscopy. In the light of the presented results, tetrameric Pd^II species can be assumed to co-exist as a second species in many cases where by current knowledge only a dimeric compound would be expected.