Difluorochloronium(III) Fluoridometallates – from Molecular Building Blocks to (Helical) Chains

Benjamin Scheibe,Antti J Karttunen,Florian Kraus,Ralf Haiges,Karl O Christe,Ulrich Müller,Sergei I Ivlev

doi:10.1002/ejic.202000845

Abstract

Difluorochloronium(III) compounds were synthesized from the reaction of metal powders (Ru, Os, Ir, Au), metal fluorides (NbF5, SbF3, BiF5) or a metal chloride (TaCl5) with excess liquid chlorine trifluoride. The compounds ClF2[AuF4], ClF2[MF6] (M = Nb, Ta, Ru, Os, Ir, Sb, Bi) and ClF2[Ta2F11] were obtained in crystalline form and their crystal structures were determined by single‐crystal X‐ray diffraction. The ClF2+ cations in the investigated compounds are bent, containing two strong, short, mainly covalent Cl–F bonds and two sterically active, free valence electron pairs in a pseudo‐tetrahedral arrangement. The coordination around the Cl atom is extended by two highly ionic, long fluorine bridges to neighboring fluoridometallate anions, resulting in a total coordination number of six. The crystal structures vary among the ClF2+ compounds and range from molecular building blocks, such as dimeric (ClF2[AuF4])2 and (ClF2[Ta2F11])2, to chains, some of which being helical, as in ClF2[MF6], (M = Nb, Ta, Ru, Os, Ir, Sb, Bi). Quantum‐chemical solid‐state and gas‐phase calculations were carried out to elucidate the bonding within the ClF2+ cations and their interactions with the bridging F atoms.

Highlights

Chlorine trifluoride is one of the most reactive compounds and reacts vigorously with many metals, metal oxides and especially with most organic compounds, if the reaction conditions are not well controlled.[1,2,3,4] The reactivity of ClF3 at ambient temperature surpasses that of elemental fluorine
Difluorochloronium(III) compounds were synthesized from the reaction of metal powders (Ru, Os, Ir, Au), metal fluorides (NbF5, SbF3, BiF5) or a metal chloride (TaCl5) with excess liquid chlorine trifluoride
The compounds ClF2[AuF4], ClF2[MF6] (M = Nb, Ta, Ru, Os, Ir, Sb, Bi) and ClF2[Ta2F11] were obtained in crystalline form and their crystal structures were determined by single-crystal X-ray diffraction

Summary

Introduction

Chlorine trifluoride is one of the most reactive compounds and reacts vigorously with many metals, metal oxides and especially with most organic compounds, if the reaction conditions are not well controlled.[1,2,3,4] The reactivity of ClF3 at ambient temperature surpasses that of elemental fluorine. If ClF3 is used in excess and reacted with a fluoride that has an appreciable fluoride ion affinity, such as AsF5 or SbF5, a difluorochloronium(III) compound is formed.[9,10] With weaker Lewis acids, such as BF3 and PF5, thermally unstable ClF2+ salts, are formed.[11] This amphoteric character is common for all halogen trifluorides, XF3 (X = Cl, Br, I). One of the authors (KOC) has demonstrated in classified unpublished work at Rocketdyne the potential of ClF2+ salts as an incendiary for Diesel fuel

Results and Discussion

A Short Introduction to the Symmetry of Polymeric Chainlike Molecules

Conclusion