Reduction of tetrakis(trimethylsilyl)ethylene with excess lithium gave a stable dianion, the first dianion of nonconjugated olefin. NMR characteristics as well as quenching experiments are described.
6Li and 13C NMR spectra of 1,2-dilithio[tetrakis(trimethylsilyl)]ethane revealed a doubly bridged π-structure in aromatic solvents similar to that observed in the crystals. However, the dianion in THF, which was found to exist as a solvent–separated ion pair of Li+(THF)4 and a species bridged by one Li atom, was reactive to undergo anionic rearrangement.
A Planar Five‐Membered Aromatic Ring Stabilized by Only Two π‐Electrons
作者:Oleksandr Kysliak、Simon H. F. Schreiner、Niklas Grabicki、Phil Liebing、Florian Weigend、Oliver Dumele、Robert Kretschmer
DOI:10.1002/anie.202206963
日期:2022.8
past, two π-electrons are just enough to stabilize five-membered aromatic compounds that are even stable at room-temperature, as shown by the facile synthesis of a dipotassium cyclopentagallene. This compound is a unique example of a five-membered aromatic ring stabilized by only two π-electrons. Single-crystal X-ray diffraction revealed a planar Ga5 ring with almost equal gallium–gallium bond lengths
尽管过去受到质疑,但两个 π 电子足以稳定甚至在室温下也稳定的五元芳香族化合物,如环五加仑子二钾的轻松合成所示。该化合物是仅由两个 π 电子稳定的五元芳环的独特例子。单晶 X 射线衍射揭示了平面 Ga 5环,其镓-镓键长几乎相等。