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★声明：本文仅代表个人观点，笔者学识有限，资料整理过程中难免存在疏漏谬误，请不吝指正。 正丁基锂晶体培养与测试操作 之前的推文“正丁基锂和叔丁基锂晶体结构”中有小伙伴好奇正丁基锂 [1]（nBuLi, normal-butyllithium, CAS: 109-72-8, CCDC [2]: 1263904）晶体培养和单晶X射线衍射实验操作，其实论文中有说明，笔者将其整理如下，仅供参考。 | For the crystallization, a temperature was chosen at which the nearly saturated solutions could be prepared; this should be as low as possible to avoid phase transitions during low temperature data collection (here: –90 ℃). The limiting values taken into account were the melting point of nBuLi (–90 ℃ according to reference [3]; the melting point of the crystals investigated here, however, was –34(2) ℃). To achieve a gradual and controlled crystallization period was extended to one week by redissolving crystals formed initially, thus leaving a small number of nucleation sites in the solution. This technique appears to increase the probability of forming single crystals suitable for X-ray crystallography [4]. During the preparation of crystals for data collection (selecting and mounting a crystal and transporting it to the diffractometer) the temperature of a sample never exceeded –45 ℃. This was facilitated by using apparatus developed for mounting crystals at low temperatures [5]. Thus the crystals could be kept at –60 ℃ on the polarization microscope slide, and then transferred to the diffractometer with a portable liquid nitrogen evaporator (see also ref. [6]). The use of inert gas Schlenk techniques and sealing with inert oil [5] were necessary to prevent the extremely oxygen and moisture-sensitive crystals from reacting with air. | 对于结晶，选择可以制备接近饱和溶液的温度，该温度应尽可能低，从而避免在低温（此处为–90 ℃）数据收集过程中发生相变。考虑的极限值是正丁基锂的熔点（根据参考文献 [3]是–90 ℃，但本研究中晶体熔点为–34(2) ℃）。为实现渐进和受控结晶周期，通过重新溶解最初形成的晶体，将结晶周期延长至一周，从而在溶液中留下少量成核位点。这种技术似乎增加了形成适用于X射线晶体学的单晶的可能性 [4]。在为数据收集准备晶体的过程中（选择和安装并将晶体运送到单晶仪），样品温度从未超过–45 ℃。通过使用为在低温下安装晶体而开发的设备 [5]实现了这一点。因此，晶体可以在偏光显微镜载玻片上保持在–60 ℃，然后用便携式液氮蒸发器转移到衍射仪上（另见参考文献 [6]）。使用惰性气体Schlenk技术和惰性油密封 [5]是必要的，这可以防止对水氧敏感的晶体与空气发生反应。 |
参考文献 [1] Kottke,T.; Stalke, D. Structures of Classical Reagents in Chemical Synthesis: (nBuLi)6,(tBuLi)4, and the Metastable (tBuLi·Et2O)2. Angew.Chem. Int. Ed. 1993,32, 580–582. DOI: 10.1002/anie.199305801. [2] (a)Allen, F. H. The Cambridge Structural Database: A Quarter of a Million CrystalStructures and Rising. Acta Cryst. 2002, B58, 380–388. DOI:10.1107/S0108768102003890. (b) Groom, C. R.; Bruno, I. J.; Lightfoot, M.P.; Ward, S. C. The Cambridge Structural Database. Acta Cryst. 2016, B72, 171–179. DOI:10.1107/S2052520616003954. (c) Mitchell, J.; Robertson, J. H.; Raithby,P. R. Cambridge Crystallographic Data Centre (CCDC). Comprehensive Coordination Chemistry III 2021, 413–437. DOI:10.1016/B978-0-12-409547-2.14829-2. [3] Wakefield,B. J. The Chemistry of Organolithium Compounds, Pergamon, Oxford, 1974. [4] McPherson,A.; in Preparation and Analysis of Protein Crystals, Wiley Interscience,New York, 1982. [5] Kottke,T.; Stalke, D. Crystal Handling at Low Temperature. J. Appl. Cryst. 1993,26, 615–619. DOI: 10.1107/S0021889893002018. [6] Veith,M.; Frank, W. Low-Temperature X-ray StructureTechniques for the Characterization of Thermolabile Molecules. Chem. Rev.1988, 88, 81–92. DOI: 10.1021/cr00083a004.
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