Structure, Bonding, and Reactivity of Room-Temperature-Stable Lithium Chloride Carbenoids

Electronic
stabilization of the negative charge by a thiophosphinoyl
and pyridyl/quinolyl substituent allows for the isolation of two lithium
chloride carbenoids at room temperature. Molecular structure analysis
by X-ray crystallography and multinuclear NMR spectroscopy reveal
no direct lithium–carbon interaction in the solid state and
in solution. This leads to remarkable thermal stability but also to
a reduced ambiphilic character of the compounds. Thus, properties
typically observed for nonstabilized Li/Cl carbenoids are less pronounced.
Nevertheless, computational studies still show that despite the charge
delocalization within the compound a high negative charge remains
at the carbenoid carbon atom. Preliminary reactivity studies confirm
this nucleophilic character and show that the carbenoids can still
be used as a “carbene” source for the formation of carbene
complexes.

通过硫代次膦酰基（thiophosphinoyl）与吡啶基/喹啉基取代基对负电荷的电子稳定作用，可在室温下分离得到两种氯化锂类卡宾（carbenoid）。通过X射线晶体衍射（X-ray crystallography）与多核核磁共振波谱（multinuclear NMR spectroscopy）进行的分子结构分析显示，无论是在固态还是溶液中，该类化合物均不存在直接的锂-碳相互作用。这一特性赋予化合物优异的热稳定性，但同时也削弱了其两亲性。因此，非稳定化Li/Cl类卡宾通常所具备的特性在该类化合物中表现得并不显著。尽管如此，计算研究仍表明，尽管化合物内部存在电荷离域（charge delocalization），类卡宾碳原子仍保留较高的负电荷。初步反应性研究证实了这一亲核特性，并表明此类类卡宾仍可作为"卡宾"源用于卡宾配合物的合成。