As described in the Introduction, we became interested in the existing literature for the crystallization behavior of (±)-[Co(en)3]I3·H2O and the absolute configuration of its enantiomers because of our project on the historical sequence of chemical studies leading Werner to formulate his Theory of Coordination Chemistry. In so doing, we discovered a number of interesting facts, including the possibility that the published “Pbca” structure of the (±)-[Co(en)3]I3·H2O was incorrect, and that it really crystallizes as a kryptoracemate in space group P212121. Other equally interesting facts concerning the crystallization behavior of [Co(en)3]I3·H2O are detailed below, together with an explanation why Platon incorrectly selects, in this case, the space group Pbca instead of the correct choice, P212121. As for the Flack parameter, (±)-[Co(en)3]I3·H2O provides an example long sought by Flack himself – a challenging case, differing from the norm. For that purpose, data sets (for the pure enantiomer and for the racemate) were collected at 100 K with R-factors of 4.24 and 2.82%, respectively, which are ideal for such a test. The fact that Pbca is unacceptable in this case is documented by the results of Second-Harmonic Generation experiments. CCDC nos: 1562401 for compound (I) and 1562403 for compound (II).

中文翻译：

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重新审视 (±)-[Co(en)3]I3·H2O 的结构 – X 射线晶体学和二次谐波结果

如引言中所述，我们对 (±)-[Co(en) 的结晶行为的现有文献产生了兴趣3]我3·H2O 及其对映异构体的绝对构型，因为我们关于化学研究历史序列的项目导致 Werner 制定了他的配位化学理论。在这样做的过程中，我们发现了许多有趣的事实，包括发表的“铅酸铅” (±)-[Co(en) 的结构3]我3·H2O 是不正确的，它确实在空间群中结晶为氪外酰胺磷212121. 关于 [Co(en) 的结晶行为的其他同样有趣的事实3]我3·H2下面详细说明 O，并解释为什么 P拉顿在这种情况下，错误地选择了空间群铅酸铅而不是正确的选择，磷212121. 至于 Flack 参数，(±)-[Co(en)3]我3·H2O 提供了一个 Flack 本人长期寻求的例子——一个具有挑战性的案例，不同于常规。为此，在 100 K 下收集数据集（纯对映异构体和外消旋体）R- 分别为 4.24% 和 2.82% 的因子，非常适合此类测试。事实是铅酸铅在这种情况下是不可接受的，这是由二次谐波产生实验的结果记录的。CCDC 编号：1562401 化合物 (I) 和 1562403 化合物 (II)。