Enantiospecific Syntheses of Copper Cubanes, Double-Stranded Copper/Palladium Helicates, and a (Dilithium)–Dinickel Coronate from Enantiomerically Pure Bis-1,3-diketones—Solid-State Self-Organization Towards Wirelike Copper/Palladium Strands
✍ Scribed by Rolf W. Saalfrank; Christine Spitzlei; Andreas Scheurer; Harald Maid; Frank W. Heinemann; Frank Hampel
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 754 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
Enantiomerically pure, vicinal diols 1 afforded in a two‐step synthesis (etherification and subsequent Claisen condensation) chiral bis‐1,3‐diketones H~2~L^(S,S)^ (3 a–c) with different substitution patterns. Reaction of these C~2~‐symmetric ligands with various transition‐metal acetates in the presence of alkali ions generated distinct polynuclear aggregates 4–8 by diastereoselective self‐assembly. Starting from copper(II) acetate monohydrate and depending on the ratio of transition‐metal ion to alkali ion to ligand, chiral tetranuclear copper(II) cubanes (C,C,C,C)‐[Cu~4~(L^(S,S)^)~2~(OMe)~4~] (4 a–c) or dinuclear copper(II) helicates (P)‐[Cu~2~(L^(S,S)^)~2~] (5) could be synthesized with square‐pyramidal and square‐planar coordination geometry at the metal center. In analogy to the last case, with palladium(II) acetate double‐stranded helical systems (P)‐[Pd~2~(L^(S,S)^)~2~] (6,7) were accessible exhibiting a linear self‐organization of ligand‐isolated palladium filaments in the solid state with short inter‐ and intramolecular metal distances. Finally, the introduction of hexacoordinate nickel(II) in combination with lithium hydroxide monohydrate and chiral ligand H~2~L^(S,S)^ (3 a) allowed the isolation of enantiomerically pure dinuclear nickel(II) coronate [(Li⋅MeOH)~2~⊂{(Δ,Λ)‐Ni~2~(L^(S,S)^)~2~(OMe)~2~}] (8) with two lithium ions in the voids, defined by the oxygen donors in the ligand backbone. The high diastereoselectivity, induced by the chiral ligands, during the self‐assembly process in the systems 4–8 could be exemplarily proven by circular dichroism spectroscopy for the synthesized enantiomers of the chiral copper(II) cubane 4 a and palladium(II) helicate 6.