X-ray Crystal Structures of [XF6][Sb2F11] (X = Cl, Br, I); 35,37Cl, 79,81Br, and 127I NMR Studies and Electronic Structure Calculation

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• 作者：John F. Lehmann ; Gary J. Schrobilgen ; Karl O. Christe ; Andreas Kornath ; and Reijo J. Suontamo
• 刊名：Inorganic Chemistry
• 出版年：2004
• 出版时间：November 1, 2004
• 年：2004
• 卷：43
• 期：22
• 页码：6905 - 6921
• 全文大小：277K
• 年卷期：v.43,no.22(November 1, 2004)
• ISSN：1520-510X

文摘

The single-crystal X-ray structures of [XF₆][Sb₂F₁₁] (X = Cl, Br, I) have been determined and represent the firstdetailed crystallographic study of salts containing the XF₆⁺ cations. The three salts are isomorphous and crystallizein the monoclinic space group P2₁/n with Z = 4: [ClF₆][Sb₂F₁₁], a = 11.824(2) Å, b = 8.434(2) Å, c = 12.088(2)Å, ages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 97.783(6)ages/entities/deg.gif">, V = 1194.3(4) ų, R₁ = 0.0488 at -130 ages/entities/deg.gif">C; [BrF₆][Sb₂F₁₁], a = 11.931(2) Å, b = 8.492(2)Å, c = 12.103(2) Å, ages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 97.558(4)ages/entities/deg.gif">, V = 1215.5(4) ų, R₁ = 0.0707 at -130 ages/entities/deg.gif">C; [IF₆][Sb₂F₁₁], a = 11.844(1) Å,b = 8.617(1) Å, c = 11.979(2) Å, ages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 98.915(2)ages/entities/deg.gif">, V = 1207.8(3) ų, R₁ = 0.0219 at -173 ages/entities/deg.gif">C. The crystalstructure of [IF₆][Sb₂F₁₁] was also determined at -100 ages/entities/deg.gif">C and was found to crystallize in the monoclinic spacegroup P2₁/m with Z = 4, a = 11.885(1) Å, b = 8.626(1) Å, c = 12.000(1) Å, ages/gifchars/beta2.gif" BORDER=0 ALIGN="middle"> = 98.44(1), V = 1216.9(2) ų,R₁ = 0.0635. The XF₆⁺ cations have octahedral geometries with average Cl-F, Br-F, and I-F bond lengths of1.550(4), 1.666(11) and 1.779(6) [-173 ages/entities/deg.gif">C]/1.774(8) [-100 ages/entities/deg.gif">C] Å, respectively. The chemical shifts of the centralquadrupolar nuclei, ^35,37Cl, ^79,81Br, and ¹²⁷I, were determined for [ClF₆][AsF₆] (814 ppm), [BrF₆][AsF₆] (2080 ppm),and [IF₆][Sb₃F₁₆] (3381 ppm) in anhydrous HF solution at 27 ages/entities/deg.gif">C, and spin-inversion-recovery experiments wereused to determine the T₁-relaxation times of ³⁵Cl (1.32(3) s), ³⁷Cl (2.58(6) s), ⁷⁹Br (24.6(4) ms), ⁸¹Br (35.4(5) ms),and ¹²⁷I (6.53(1) ms). Trends among the central halogen chemical shifts and T₁-relaxation times of XF₆⁺, XO₄^-,and X^- are discussed. The isotropic ¹J-coupling constants and reduced coupling constants for the XF₆⁺ cationsand isoelectronic hexafluoro species of rows 3-6 are empirically assessed in terms of the relative contributions ofthe Fermi-contact, spin-dipolar, and spin-orbit mechanisms. Electronic structure calculations using Hartree-Fock,MP2, and local density functional methods were used to determine the energy-minimized gas-phase geometries,atomic charges, and Mayer bond orders of the XF₆⁺ cations. The calculated vibrational frequencies are in accordwith the previously published assignments and experimental vibrational frequencies of the XF₆⁺ cations. Bondingtrends within the XF₆⁺ cation series have been discussed in terms of natural bond orbital (NBO) analyses, theligand close-packed (LCP) model, and the electron localization function (ELF).