Second‐Sphere Coordination–a Novel Rǒle for Molecular Receptors

Abstract

“Supramolecules”—adducts formed between transition‐metal complexes and neutral compounds—have long been known; their structures and bonding patterns have been elucidated in recent years by X‐ray structure analysis and NMR spectroscopy. 1 is cationic Pt complex in which the [18]crown‐6 is bound in the second sphere through hydrogen bonds. Applications of the concept of binding in the second coordination sphere have ben found in such distinct areas as analytical chemistry and the controlled release of medicaments. (Figure Presented.)