Chair of Inorganic Chemistry II, Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, 44801, Bochum, Germany.
Chemistry. 2023 Jun 2;29(31):e202300504. doi: 10.1002/chem.202300504. Epub 2023 Apr 20.
Owing to the strong electron-donating ability of ylide substituents, diylidyltetrylenes are usually highly nucleophilic species with strong donor capacities. Here, we demonstrate that their electronic properties are in fact highly flexible and can be effectively tuned through variation of the substituent in the ylide backbone. Initial density functional theory studies showed that cyano groups are particularly capable in lowering the LUMO energy of diylidyl germylenes thus turning these usually highly nucleophilic species into electrophilic compounds. This was confirmed by experimental studies. Attempts to synthesize the germylene (Y ) Ge [with Y =Ph P-(C)-CN] from the corresponding metalated ylide Y K selectively led to germanide [(Y ) Ge)K] thus reflecting the electrophilic nature of the intermediate formed germylene. XRD analysis of single crystals of (Y ) Ge - serendipitously obtained through protonative cleavage of one ylide from the germanide - revealed a monomeric structure with rather long Ge-ylide linkages, which corroborates well with a pure single bond and no stabilization of the empty p orbital at germanium through π bonding. The germanide exhibits methanide-like reactivity towards chalcogens but a likewise weak Ge-C bond as demonstrated by the insertion of carbon dioxide.
由于叶立德取代基的强给电子能力，二芳基二硅烯通常是具有强给电子能力的高亲核性物种。在这里，我们证明它们的电子性质实际上是高度灵活的，可以通过改变叶立德主链中的取代基来有效调节。最初的密度泛函理论研究表明，氰基特别能够降低二芳基锗叶立德的 LUMO 能量，从而将这些通常高亲核性的物种转化为亲电性化合物。这一点通过实验研究得到了证实。从相应的金属化叶立德 Y K 中尝试合成锗叶立德（Y）Ge[其中 Y = Ph P-(C)-CN]，选择性地得到了锗化物[(Y)Ge)K]，从而反映了形成的锗叶立德中间体的亲电性。通过质子化从锗化物中裂解一个叶立德偶然获得的（Y）Ge 单晶的 XRD 分析表明，其具有相当长的 Ge-叶立德键的单体结构，这与纯单键很好地吻合，并且通过π键没有稳定硅上的空 p 轨道。该锗化物表现出类似于甲硅烷的反应性，可与硫属元素反应，但与二氧化碳的插入一样，Ge-C 键也同样较弱。
