Homeomorphic Isomerization as a Design Element in Container Molecules; Binding, Displacement, and Selective Transport of MCl2 Species (M = Pt, Pd, Ni)

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• 作者：Sugam KharelHemant Joshi ; Stephen BierschenkMichael Stollenz ; Deeb Taher ; Nattamai Bhuvanesh ; John A. Gladysz
• 刊名：Journal of the American Chemical Society
• 出版年：2017
• 出版时间：February 15, 2017
• 年：2017
• 卷：139
• 期：6
• 页码：2172-2175
• 全文大小：382K
• ISSN：1520-5126

文摘

The dibridgehead diphosphine ((CH₂)₁₄)₃P (1) can rapidly turn inside-out (homeomorphic isomerization) to give a mixture of in,in and out,out isomers. The exo directed lone pairs in the latter are able to scavenge Lewis acidic MCl₂; cagelike adducts of the in,in isomer, trans-Cl₂(P((CH₂)₁₄)₃P) (M = 2/Pt, 3/Pd, 4/Ni), then form. The NiCl₂ unit in 4 may be replaced by PtCl₂ or PdCl₂, but 2 and 3 do not give similar substitutions. U-tubes are charged with CH₂Cl₂ solutions of 1 (lower phase), an aqueous solution of K₂MCl₄ (charging arm; M = Pt, Pd), and an aqueous solution of excess KCl (receiving arm). The MCl₂ units are then transported to the receiving arm until equilibrium is reached (up to 22 d). When the receiving arm is charged with KCN, transport is much faster (ca. 100 h) and higher K₂MX₄ equilibrium ratios are obtained (≥96≤4). Analogous experiments with K₂PtCl₄/K₂PdCl₄ mixtures show PdCl₂ transport to be more rapid. A similar diphosphine with longer methylene chains, P((CH₂)₁₈)₃P, is equally effective. No transport occurs in the absence of 1, and other diphosphines or monophosphines assayed give only trace levels.