Photochemical Synthesis and Characterization of Xenon(VI) Hexafluoridomanganates(IV)

Abstract

Reactions between XeF2, MnF3 and UV‐irradiated elemental F2 in anhydrous HF have yielded [XeF5]2[MnF6] and XeF5MnF5; meanwhile, [XeF5]4[Mn8F36] has been observed as a minor phase upon the crystallization of the product obtained by fluorination of an n(XeF2)/n(MnF3) = 1:3 mixture in the presence of an UV source. The crystal structure of [XeF5]2[MnF6] is isotypic with the known [XeF5]2[PdF6]. Its asymmetric structural unit consists of two crystallographically unique [XeF5]+ cations and a [MnF6]2– anion. The single‐crystal structure determination of XeF6·2MnF4 reveals that it is better formulated as [XeF5]4[Mn8F36]. Discrete octameric [Mn8F36]4– anions are built from eight MnF6 octahedra, each sharing three vertices, in the shape of a ring, which is different from the previously known cubic [Ti8F36]4– anion. The main structural feature of the anionic part of the crystal structure of [XeF5][MnF5] (determined from both X‐ray single‐crystal and synchrotron X‐ray powder diffraction data) is infinite zigzag chains of distorted MnF6 octahedra that share cis vertices. [XeF5][MnF5] is paramagnetic in the 296–200 K temperature range, with a Curie constant of C = 1.87 emu K mol–1 (µeff = 3.87 µB) and a Curie–Weiss temperature of θ = –9.3 K. Below 100 K, there is weak antiferromagnetic coupling between the MnIV ions, with a coupling constant of J = –1.3 cm–1. Raman spectra showed that [XeF5]2[MnF6] decomposes at ambient temperature in a He–Ne laser beam (power > 1.7 mW) to [XeF5][MnF5], with further decomposition to MnF3.