The syntheses of three series of complexes designed with self-complementary motifs for formation of halogen bonds between an iodotetrafluorophenyl ligand and a halide ligand at square-planar nickel are reported, allowing structural comparisons of halogen bonding between all four halides C₆F₄I⋯X–Ni (X = F, Cl, Br, I). In the series trans-[NiX(2,3,5,6-C₆F₄I)(PEt₃)₂] 1pX and trans-[NiX(2,3,4,5-C₆F₄I)(PEt₃)₂] (X = F, Cl, Br, I) 1oX, the iodine substituent on the benzene ring was positioned para and ortho to the metal, respectively. The phosphine substituents were varied in the series, trans-[NiX(2,3,5,6-C₆F₄I)(PEt₂Ph)₂] (X = F, I) 2pX. Crystal structures were obtained for the complete series 1pX, and for 1oF, 1oCl, 1oI and 2pI. All these complexes exhibited halogen bonds in the solid state, of which 1pF exhibited unique characteristics with a linear chain, the shortest halogen bond d(C₆F₄I⋯F–Ni) = 2.655(5) Å and the greatest reduction in halogen bond distance (I⋯F) compared to the sum of the Bondi van der Waals radii, 23%. The remaining complexes form zig-zag chains of halogen bonds with distances also reduced with respect to the sum of the van der Waals radii. The magnitude of the reductions follow the pattern F > Cl ∼ Br > I, 1pX > 1oX, consistent with the halogen bond strength following the same order. The variation in the I⋯X–Ni angles is consistent with the anisotropic charge distribution of the halide ligand. The temperature dependence of the X-ray structure of 1pF revealed a reduction in halogen bond distance of 0.055(7) Å on cooling from 240 to 111 K. Comparison of three polymorphs of 1oI shows that the halogen bond geometry may be altered significantly by the crystalline environment. The effect of the halogen bond on the ¹⁹F NMR chemical shift in the solid state is demonstrated by comparison of the magic-angle spinning NMR spectra of 1pF and 1oF with that of a complex incapable of halogen bond formation, trans-[NiF(C₆F₅)(PEt₃)₂] 3F. Halogen bonding causes deshielding of δ_iso in the component of the tensor perpendicular to the nickel coordination plane. The results demonstrate the potential of fluoride ligands for formation of halogen bonds in supramolecular structures.

中文翻译：

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自互补卤化镍可对分子间卤素键进行多方面比较：氟化物配体与其他卤化物† •

报道了设计有自我互补基序的三个系列配合物的合成，这些配合物用于在方形镍平面上形成碘四氟苯基配体和卤化物配体之间的卤素键，从而可以比较所有四个卤化物C ₆ F ₄ I⋯之间的卤素键结构X–Ni（X = F，Cl，Br，I）。在系列反式-[NiX（2,3,5,6-C ₆ F ₄ I）（PEt ₃）₂ ] 1pX和反式-[NiX（2,3,4,5-C ₆ F ₄ I）（ PEt ₃）₂ ]（X = F，Cl，Br，I）1oX，苯环上的碘取代基分别位于金属的对位和邻位。膦取代基以反-[NiX（2,3,5,6-C ₆ F ₄ I）（PEt ₂ Ph）₂ ]（X = F，I）2pX的序列变化。获得了完整系列1pX，1oF，1oCl，1oI和2pI的晶体结构。所有这些配合物在固态下均表现出卤素键，其中1pF具有线性链的独特特性，最短的卤素键d（C ₆ F ₄ I⋯F–Ni）= 2.655（5）Å，并且与邦迪范德华半径之和相比，卤素键距（I⋯F）的减少最大。其余的配合物形成卤素键的Z字形链，距离相对于范德华半径之和也减小。减少的幅度遵循模式F> Cl〜Br > I，1pX > 1oX，这与遵循相同顺序的卤素键强度一致。I⋯X-Ni角的变化与卤化物配体的各向异性电荷分布是一致的。1pF的X射线结构的温度依赖性结果表明，从240 K冷却至111 K时，卤素键的距离减小了0.055（7）Å。三种1oI多晶型物的比较表明，结晶环境可能会极大地改变卤素键的几何形状。上的卤键的效果¹⁹在固态F NMR化学位移是由魔角自旋的NMR谱的比较表明为1pF和10f中与该的卤素键形成复合物裁断的反式[NIF（C - ₆ F ₅）（PEt ₃）₂ ] 3F。卤键的原因去屏蔽的δ_异在张量分量中垂直于镍配位平面。结果表明氟化物配体在超分子结构中形成卤素键的潜力。