A Highly Effective Strategy for Encapsulating Potassium Cations in Small Crown Ether Rings on a Dinuclear Palladium Complex

Abstract

The potential of 15-crown-5 ethers to link large cations, such as potassium, is limited by the quasi-parallel arrangement of two oxygen donor moieties upon appropriate orientation of the corresponding ether-ring-containing molecules. Substrates bearing the two crown ethers that are capable of achieving such coordination are hitherto unknown. The synthesis and isolation of a tailor-made dinuclear palladacycle bearing 15-crown-5 ether rings on the metallated phenyls offers such a possibility, providing the adequate environment for the formation of the sandwiched [K(metallacycle-15-crown-5) ] moiety. This synthetic strategy also culminates in the isolation of the first palladacycle able to entrap a potassium cation through bonding to two 15-crown-5 ether rings in a single molecule.

From Chemical Serendipity to Translational Chemistry: New Findings in the Reactivity of Palladacycles

“…Then, our ensuing hypothesis was that adequately separating the two pairs of parallel metallated moieties should produce the needed arrangement, giving molecules that are appropriate for sandwiched potassium coordination through several reaction steps. But, again, this was not the case, and what we found was that the desired compound could be made in a one‐pot reaction to give coordinated potassium in small crown ether rings (Scheme ) …”

“…Reproduced with permissionfrom Ref. [34].C opyright 2017 Wiley-VCHV erlag GmbH &C o. KGaA. ChemistryOpen 2018, 7,754 -763 www.chemistryopen.org 2018 The Authors.…”

“…Reproduced with permission from Ref. [34].Copyright2 017 Wiley-VCH Verlag GmbH &Co. KGaA. Figure 13.…”

“…But, again, this was not the case, and what we found was that the desired compound could be made in a one-pot reactiontog ive coordinated potassium in small crown ether rings (Scheme 7). [34] This process culminates in the isolation of au nique dinuclear phosphine-bridged thiosemicarbazone palladacycle con-taining1 5-crown-5 ether rings on the metallated phenyls, capable of coordinating to the K + cation by sandwichingi tb etween the two ether rings, which results in at rinuclearm ixed main group-transition metal complex. This result represents a furthere nrichment in the chemistry of palladacycles as well as in the coordination chemistry of crown ethers.…”

Entropy‐Driven Reversible Agglomeration of Crown Ether Capped Gold Nanoparticles

“…Crown ethers, which are cyclic oligomers of ethylene oxide, are known for their ability to strongly bind to specific cations, while being completely inert to others. This unique property is due to the hole‐size cation‐diameter relationship and has resulted in their use for a variety of applications such as sensing, phase transfer catalysis and ion encapsulation . With particular note given to Kotov and co‐workers, who developed long chain 18‐Crown‐6 capped AuNPs capable of detecting melamine through a similar agglomeration effect as described here.…”