Solid-state NMR spectroscopic study of coordination compounds of XeF2 with metal cations and the crystal structure of [Ba(XeF2)5][AsF6]2

The coordination compounds [Mg(XeF2)(2)][AsF6](2), [Mg(XeF2)(4)][AsF6](2), [Ca(XeF2)(2.5)][AsF6](2), [Ba(XeF2)(3)][AsF6](2), and [Ba(XeF2)(5)][AsF6](2) were characterized by solid-state F-19 and Xe-129 magic-angle spinning NMR spectroscopy. The F-19 and Xe-129 NMR data of [Mg(XeF2)(2)][AsF6](2), [Mg(XeF2)(4)][AsF6](2), and [Ca(XeF2)(2.5)][AsF6](2) were correlated with the previously determined crystal structures. The isotropic F-19 chemical shifts and (1)J(Xe-129-F-19) coupling constants were used to distinguish the terminal and bridging coordination modes of XeF2. Chemical-shift and coupling-constant calculations for [Mg(XeF2)(4)][AsF6](2) confirmed the assignment of terminal and bridging chemical-shift and coupling-constant ranges. The NMR spectroscopic data of [Ba(XeF2)(3)][AsF6](2) and [Ba(XeF2)(5)][AsF6](2) indicate the absence of any terminal XeF2 ligands, which was verified for [Ba(XeF2)(5)][AsF6](2) by its X-ray crystal structure. The adduct [Ba(XeF2)(5)][AsF6](2) crystallizes in the space group Fmmm, with a = 11.6604(14) A, b = 13.658(2) A, c = 13.7802(17) A, V = 2194.5(5) A(3) at -73 degrees C, Z = 4, and R = 0.0350 and contains two crystallographically independent bridging XeF2 molecules and one nonligating XeF2 molecule. The AsF6- anions in [Mg(XeF2)(4)][AsF6](2), [Ca(XeF2)(2.5)][AsF6](2), [Ba(XeF2)(3)][AsF6](2), and [Ba(XeF2)(5)][AsF6](2) were shown to be fluxional with the fluorines-on-arsenic being equivalent on the NMR time scale, emulating perfectly octahedral anion symmetry.