Siliciumanaloga von Kronenethern und Cryptanden: ein neues Kapitel in der Wirt‐Gast‐Chemie?

Abstract

Kronjuwelen: Der gezielte Einsatz von schwach koordinierenden Anionen hat kürzlich zur ersten Direktsynthese von Alkalimetallkomplexen von siliciumbasierten Kronenethern und Cryptanden geführt. Diese Ergebnisse geben den Gebieten der Wirt‐Gast‐Chemie, der anorganischen Ringtransformationen und der Ringöffnungspolymerisation neue Impulse.

Gas‐Phase Selective Oxidation of Benzyl Alcohol to Benzaldehyde with Molecular Oxygen over Unsupported Nanoporous Gold

“…[2, 3] Die zunächst erwartete Koordination der Siloxansauerstoffatome an die Metallionen konnte jedoch in keinem der Metallderivate von 1 beobachtet werden. Dies ist auf die ausgesprochen geringe Lewisbasizität von Siloxanen zurückzuführen 4…”

The Selenium‐Based Hexameric Macrocycle [(Se)P(μ‐NtBu)2P(μ‐Se)]6

“…[1,2] The tetrameric, nitrogen-bridged macrocycle [{P(m-NtBu)} 2 (m-NH)] 4 (Scheme 1 a) is obtained by the condensation of the dimers [ClP(m-NtBu)] 2 and [(NH 2 )P-(m-NtBu)] 2 in the presence of Et 3 N.[3] However, the pentameric homologue is produced exclusively if this reaction is undertaken in the presence of I À ions, resulting in the hostguest complex [{P(m-NtBu)} 2 (m-NH)] 5 I À (Scheme 1 b).[4] The toroidal structures of the tetramer and pentamer and the presence of endo NÀH functionalities combine the appearance and host-guest characteristics of organic macrocycles such as calixarenes and porphyrins.Less progress has been made in attempts to extend this class of new ligands to macrocycles containing other bridging elements, owing largely to the inability to generalize the synthetic methods used for N-bridged species. Indeed, the only representative of this type reported to date is the oxygenbridged dimer [{P(m-N(2-py)} 2 (m-O)] 2 (2-py = 2-pyridyl), obtained by hydrolysis of [ClP{m-N(2-py)}] 2 in the presence of CuCl and pyridine.…”

Hybrid Disila-Crown Ethers as Hosts for Ammonium Cations: The O–Si–Si–O Linkage as an Acceptor for Hydrogen Bonding

“…Geometric criteria for the search were similar to those in ref [21]. CCDC ConQuest Version 1.19 was used for the search; 2 See Scheme 1 for abbreviations; 3 Subscript E denotes that the hydrogen bonding refers to an etheric oxygen atom: two carbon atoms are located next to one oxygen atom; 4 * = published within this work.…”

“…These interactions are understood as a donation of electron density in the case p(O) → σ*(Si-C), which is competing with the coordination towards a Lewis acid and vice versa. Hence, the basicity of silicon bonded oxygen atoms turns out to be lower [3][4][5]. The other explanatory model considers the Si-O bond as highly ionic.…”