An Adaptable and Dynamically Porous Organic Salt Traps Unique Tetrahalide Dianions

Abstract

Bis(I2) adducts of hexamethonium dihalides are pre‐organized to respond dynamically to heating and reach a functional structure that favors the formation of the poorly stable and virtually unknown [I2Br2]2− and [I2Cl2]2− tetrahalides which could not be obtained in solution (see picture). The cavity‐directed reactivity affords new opportunities for synthesis and interconversion of polyhalogen anions.

Polyhalogen and Polyinterhalogen Anions from Fluorine to Iodine

“…The crystal packing is influenced by hydrogen bonds between the N−H groups of the cation and chlorine atoms of [I 2 Cl] − , and by many weak C−H⋅⋅⋅Hal interactions. However, the structure of [I 2 Cl] − is also known with a variety of counterions . Beyond the monocoordinated Cl − anion of [I 2 Cl] − , it is possible to extend the coordination sphere to four I 2 molecules, as seen in [Cl(I 2 ) 4 ] − , which forms a square‐planar structure .…”

Polyhalogen‐ und Polyinterhalogen‐Anionen von Fluor bis Iod

“…Die Packung im Kristall wird durch Wasserstoffbrücken zwischen den N‐H‐Gruppen des Kations und den Chlor‐Atomen in [I 2 Cl] − sowie vielen schwachen C‐H⋅⋅⋅Hal‐Wechselwirkungen beeinflusst. Die Struktur von [I 2 Cl] − ist auch mit einer Reihe von anderen Gegenionen bekannt . Über das einfach koordinierte Cl − ‐Anion von [I 2 Cl] − hinaus ist es möglich, die Koordinationssphäre auf vier I 2 ‐Moleküle zu erweitern und somit quadratisch‐planares [Cl(I 2 ) 4 ] − zu bilden .…”

“…Festkörperstrukturen wurden direkt aus Pulver‐XRD‐Daten gewonnen. Interessanterweise konnten diese Anionen bisher nicht aus Lösung erhalten werden …”

Iodine and Halogen Bonding

“…The complex is formed both from solution and from gas-solid reaction, demonstrating the dynamically porous character of bis(trimethylammonium)alkane diiodide salts. on reaction with two equivalents of I 2 , hexamethonium chloride, and bromide afford the corresponding mixed trihalides HMeT 2+ •2XI 2 − (X = Cl − , Br − ), which undergo thermally induced crystal-tocrystal elimination of one I 2 molecule, and the virtually unknown tetrahalides [Cl 2 I 2 ] 2− and [Br 2 I 2 ] 2− are obtained in quantitative yields (Scheme 8.2) [98]. Similarly, slow heating of HMeT 2+ •2I 3 − affords HMeT 2+ •[I 4 ] 2− via elimination of one I 2 molecule.…”