کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1314265 | 975957 | 2010 | 9 صفحه PDF | دانلود رایگان |
Interaction of robust chromium(III) fluoride complexes with sodium or lithium cations in solution lead to hypsochromic spectral shifts of increasing magnitude along the series: trans-[CrF2(py)4]+, mer-[CrF3(terpy)], and fac-[CrF3(Me3tacn)]. Crystalline products isolated from solution exhibit μ2-bridging by the fluoride ligands in a linear fashion between Na+-ions and chromium centres in catena-[Na(H2O)4(μ-F)-trans-{CrF(py)4}](HCO3)2 and in the dimers [Li(H2O)n(μ-F)-trans-{CrF(py)4}]2+ (n = 3, 4). The uncharged chromium complexes fac-[CrF3(Me3tacn)] and mer-[CrF3(terpy)] have been synthesized from mer-[CrF3(py)3] and shown to precipitate sodium salts from solution, of which 3[CrF3(Me3tacn)]·2Na(Bph4)·solv and 6[CrF3(terpy)]·4Na(Bph4)·solv have been crystallographically characterized. In these clusters, the neutral fluoride complexes bring the Na+ cation separation down to 3.610 Å and 3.369 Å, respectively, which is much closer than the inter-cation distance in NaCl and comparable to that of NaF. DFT calculations support the notion of a strong interaction between Na+ ions and neutral chromium(III) fluoride complexes. The calculations reproduce the magnitude and the counter-intuitive sign of the spectral shifts induced by second sphere complexation in solution, which originates in a breakdown of the assumption of parameter transferability in ligand-field descriptions.
Cationic and uncharged chromium(III)fluoride complexes interact strongly with alkali metal ions in solution as well as in the solid state. This leads to a new structure type of fluoride-bridged clusters. Spectroscopic effects of second sphere interactions are modeled and interpreted by use of DFT calculations.Figure optionsDownload as PowerPoint slide
Journal: Journal of Fluorine Chemistry - Volume 131, Issue 9, September 2010, Pages 898–906