Crystal Structures of Homoleptic Propynyloargentates AI[Ag(C3H3)2] with AI = Ag, Li, Na Solved and Refined from X‐ray Powder Diffraction Data
Crystal Structures of Homoleptic Propynyloargentates AI[Ag(C3H3)2] with AI = Ag, Li, Na Solved and Refined from X‐ray Powder Diffraction Data
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根据 X 射线粉末衍射数据解析和精炼 AI = Ag、Li、Na 的均配丙炔基银酸盐 AI[Ag(C3H3)2] 的晶体结构
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发表时间：
2014
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通讯作者：
U. Ruschewitz
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作者：
Leo Pak;B. Zibrowius;Marck Lumeij;R. Dronskowski;U. Ruschewitz
用实验室X射线粉末衍射数据（Iba ~ 2，Z = 4）解析并修正了三种同构均配丙炔基银酸盐Ag[Ag（C_3H_3）_2]，Li[Ag（C_3H_3）_2]和Na[Ag（C_3H_3）_2]的晶体结构。几乎线性的[H3C-C <$C···Ag···C <$C-CH 3]-阴离子被发现：碱金属阳离子或第二个银阳离子配位到炔配体（CN = 8）的C <$C三键上，从而形成层状结构片段，它们以AB方式沿着[100]堆叠。这些晶体结构由IR和固态NMR光谱证实。粉末SHG测量证实了偏心空间群Iba 2。另一方面，这些方法也支持了先前获得的第一个结构模型，其中在较小的晶胞（Amm 2，Z = 2）中发现了非常不寻常的弯曲[Ag（CCCH 3）2]-单元。键分析COHP计算清楚地表明，这种结构基序不能是稳定的。仔细重新检查衍射数据，现在还包括高分辨率同步加速器粉末衍射数据（HASYLAB，光束线B2），揭示了一个弱的额外反射的存在，表明一个更大的晶胞。因此，这项研究清楚地表明，在非常特定的情况下-例如，与中心金属离子相比，具有弱散射能力的配体-即使考虑到来自补充光谱方法的额外信息，也可以从X射线粉末衍射数据中获得错误的结构模型。因此，需要额外的电子结构计算来阐明正确的结构排列。
The crystal structures of three isostructural homoleptic propynyloargentates, namely Ag[Ag(C3H3)2], Li[Ag(C3H3)2], and Na[Ag(C3H3)2] were solved and refined from laboratory X-ray powder diffraction data (Iba2, Z = 4). Almost linear [H3C–C≡C···Ag···C≡C–CH3]– anions are found: The alkali metal cations or the second silver cation coordinate side-on to the C≡C triple bond of the alkyne ligand (CN = 8) so that layer-like structural fragments are formed, which are stacked in an AB fashion along [100]. These crystal structures are corroborated by IR and solid-state NMR spectra. Powder SHG measurements confirm the acentric space group Iba2. On the other hand, these methods also supported a first structural model obtained earlier, in which very unusual bent [Ag(CCCH3)2]– units were found in a smaller unit cell (Amm2, Z = 2). Bond-analytical COHP calculations clearly indicate that this structural motif cannot be stable. A close re-inspection of the diffraction data, now also including high-resolution synchrotron powder diffraction data (HASYLAB, beamline B2), reveal the existence of one weak additional reflection indicating a larger unit cell. Hence, this investigation clearly shows that under very specific circumstances – e.g. ligands with a weak scattering power compared to the central metal ion – wrong structural models can be obtained from X-ray powder diffraction data, even when additional information from complementary spectroscopic methods is taken into account. Additional electronic-structure calculations are therefore needed to elucidate the correct structural arrangement.