2-tetrelavinylides(C=EH2;E=Si,Ge)是根据量子化学研究[E,C,2H]势能超表面容易地通过反式弯曲的tetrelaxylenesHE=CH异构化为热力学上最稳定的1-tetrelavinylidenes(E=CH2)。因此,缺乏对2-tetrelavinylidenes(C=ER2)的实验研究。在此,我们报告了第一个N-杂环卡宾(NHC)负载的2-硅亚乙烯基(NHC)C=SiBr(Tbb)(1-Si:NHC=C[N(Dipp)CH]2,Dipp=2,6-二异丙基苯基,Tbb=2,6-双[双(三甲基甲硅烷基)甲基]-4-叔丁基苯基)和等价的2-胚亚烷基(NHC)C=GeBr(R)(1-Ge,1-GeMind:R=Tbb,Mind(1,1,3,3,5,5,7,7-八甲基-S-氢茚并-4-基)。使用重氮烯烃(NHC)CN2作为亚乙烯基转移试剂,从1,2-二溴二硝基烯类(E)-(R)BrE=EBr(R)获得了NHC支持的2-叔丁基亚乙烯基。1-E(E=Si,Ge)具有平面亚乙烯基核,弯曲二配位亚乙烯基碳原子(CVNL),E=CVNL键非常短,NHC五元环与亚乙烯基核的取向几乎正交。1-E电子结构的量子化学分析表明,1-tetrelaalene和tetrelyne具有明显的弯曲特性。NMR研究揭示了1-E的动力学,涉及具有低活化屏障的CVNL-CNHC键周围的NHC旋转。此外,1-E的合成潜力通过前所未有的NHC支持的溴菌BrGe=C(EBr2Tbb)(NHC)(2-SiGe:E=Si;2-GeGe:E=Ge)的合成和充分表征得到证明。
2-tetrelavinylidenes (C=EH2; E=Si, Ge) are according to quantum chemical studies the least stable isomers on the [E,C,2H] potential energy hypersurface isomerizing easily via the trans-bent tetrelaacetylenes HE≡CH to the thermodynamically most stable 1-tetrelavinylidenes (E=CH2). Consequently, experimental studies on 2-tetrelavinylidenes (C=ER2) and their derivatives are lacking. Herein we report experimental and theoretical studies of the first N-heterocyclic carbene (NHC) supported 2-silavinylidene (NHC)C=SiBr(Tbb) (1-Si: NHC=C[N(Dipp)CH]2, Dipp=2,6-diisopropylphenyl, Tbb=2,6-bis[bis(trimethylsilyl)methyl]-4-tert-butylphenyl) and the isovalent 2-germavinylidenes (NHC)C=GeBr(R) (1-Ge, 1-GeMind: R=Tbb, Mind (1,1,3,3,5,5,7,7-octamethyl-s-hydrindacene-4-yl)). The NHC-supported 2-tetrelavinylidenes were obtained selectively from the 1,2-dibromoditetrelenes (E)-(R)BrE=EBr(R) using the diazoolefin (NHC)CN2 as vinylidene transfer reagent. 1-E (E=Si, Ge) have a planar vinylidene core, a bent-dicoordinated vinylidene carbon atom (CVNL), a very short E=CVNL bond and an almost orthogonal orientation of the NHC five-membered ring to the vinylidene core. Quantum chemical analysis of the electronic structures of 1-E suggest a significantly bent 1-tetrelaallene and tetrelyne character. NMR studies shed light into the dynamics of 1-E involving NHC-rotation around the CVNL-CNHC bond with a low activation barrier. Furthermore, the synthetic potential of 1-E is demonstrated by the synthesis and full characterization of the unprecedented NHC-supported bromogermynes BrGe=C(EBr2Tbb)(NHC) (2-SiGe: E=Si; 2-GeGe: E=Ge).