Investigation of Bis(Perfluoro-tert-Butoxy) Halogenates(I/III).

Patrick Pröhm,Patrick Voßnacker,Susanne M Rupf,Willi R Berg,Sebastian Riedel

doi:10.1002/chem.202103325

Abstract

A systematic study of halogenate(I/III) anions with polyatomic ligands is presented. The bis(perfluoro‐tert‐butoxy) halogenates(I) [X(OC4F9)2]−, X=Cl, Br, I, of chlorine, bromine, and iodine are prepared as their tetraethylammonium salts and characterized with IR, Raman, and NMR spectroscopic methods, as well as single‐crystal X‐ray diffraction analyses. Spectroscopical data are supported by quantum‐chemical calculations. Additionally, the bonding situation of the species in question are analyzed and discussed. Furthermore, the oxidation to the corresponding halogenate(III) derivatives was studied. For [Br(OC4F9)2]−, oxidation with elemental fluorine gave [BrF2(OC4F9)2]−. Iodide was directly oxidized by ClOC4F9 to the IIII species [I(OC4F9)4]−, which is a surprisingly inert anion that might be used as a weakly coordinating anion (WCA) in the future. For [Cl(OC4F9)2]−, the decomposition products of the synthetic approaches towards a chlorine(III) system were analyzed.

Highlights

Halogen compounds with halogens in positive oxidation states and alcoholate ligands are rare, especially amongst the lighter halogens bromine[1,2] and chlorine.[3,4,5]
Hypochlorite is the main component of industrially used bleach[9] and its organic esters are used for synthetical purposes, for example, the synthesis of perfluorinated peroxides.[3]
While non-fluorinated hypochlorites are typically prepared in aqueous solutions, their perfluorinated counterparts are synthesized with ClF under strict exclusion of moisture

Summary

Introduction

Are known, including OMe,[4] OEt,[4] OiPr,[5] OtBu.[5]. fully fluorinated versions of these hypochlorites exist.[3]. Due to the high oxidation potential of partially positively charged halogens anions are often more stable than their neutral or cationic counterparts. It appears surprising that virtually nothing is known about such anions with the exception of a quite instable intermediate reported by Minkwitz in 1997, [NMe4][Br(OCF3)2].[11] It was synthesized via exposure of [NMe4]Br or [NMe4][BrCl2] to ClOCF3. We present the first systematic study of halogenate(I/ III) anions of chlorine, bromine and iodine using the perfluorinated OtBuF as a potent ligand system to stabilize such oxidizing compounds (Figure 1). We believe this is a fundamental work for the understanding of hypervalent halogen molecules

Results and Discussion

Conclusion

Conflict of Interest