Crystal Structure, Solubility, and Electronic Spectrum of Titanium Tetraiodide
Crystal Structure, Solubility, and Electronic Spectrum of Titanium Tetraiodide
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四碘化钛的晶体结构、溶解度和电子能谱
DOI：
10.1021/ic50197a013
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发表时间：
1979
期刊：
影响因子：
--
通讯作者：
W. F. Libby
中科院分区：
文献类型：
--
作者：
E. Tornqvist;W. F. Libby
研究了钛的两种晶型及其出现的条件。属于空间群Pa 3-Th 6的立方变体显然总是在TiI从熔体或过饱和溶液中结晶时形成。然而，这种变体在室温下是亚稳定的，并且在几天到几个月的时间内转化为具有相当复杂的X射线衍射图案的不太明确的结构，这取决于原始立方变体中晶体的尺寸和条件。在23 ℃下测定的立方晶型的晶胞尺寸对应于a. = 12.055 A，发现与以前报道的不同，在一种情况下相当可观。稳定修饰的晶面间距d也与文献中的略有不同，但无法确定确切的结构。由于立方晶型的亚稳性质，TiI，.如在有机溶剂中的溶解度，文献中报道的通常是那些稳定的改性。与文献数据相反，发现TiI的立方改性非常容易溶解，并且在烃溶剂中表现出可观的溶解度。在溶液中，TiI给出了一个非常有趣的电子光谱，这无疑是电荷转移的特征，并让人想起TiCl的报告，但与预期的更容易氧化的I-相比，C1-的吸收发生在相当高的波长。因此，在苯和环己烷中，TiI的第一个主要吸收分别发生在517和514 nm处，并且是该化合物的强烈颜色的原因。在这些波长下建立的摩尔消光系数，在苯和环己烷在23 OC的钛14的溶解度可以测定比色法，并发现分别为32.7和24.4 g/L。
The two crystalline forms of TiI, and the conditions for their appearance have been studied. The cubic modification belonging to the space group Pa3-Th6 is apparently always formed when TiI, crystallizes from the melt or from a supersaturated solution. However, this modification is metastable at room temperature and converts into a less well-defined structure with a considerably more complicated X-ray diffraction pattern within a period which may vary from a few days to some months, depending upon the size and condition of the crystals in the original cubic modification. The unit cell dimensions of the cubic form determined at 23 OC corresponding to a. = 12.055 A were found to differ from those reported previously, in one case quite appreciably. The interplanar d spacings for the stable modification also differed slightly from those in the literature, but the exact structure could not be determined. Because of the metastable character of the cubic modification, physical properties of TiI,. such as solubility in organic solvents, reported in the literature have normally been those of the stable modification. Contrary to literature data, the cubic modification of TiI, was found to dissolve very readily and to exhibit appreciable solubility in hydrocarbon solvents. In solution, TiI, gives a very interesting electronic spectrum, which is undoubtedly of charge-transfer character and is reminiscent of the one reported for TiCI, but with the absorptions occurring at considerably higher wavelengths as expected from the much more ready oxidizability of I- in comparison with C1-. Thus the first major absorption for TiI, occurs at 517 and 514 nm, in benzene and cyclohexane, respectively, and is responsible for the strong color of this compound. With the established molar extinction coefficients at these wavelengths, the solubility of Ti14 in benzene and cyclohexane at 23 OC could be determined colorimetrically and was found to be 32.7 and 24.4 g/L, respectively.