五硅环戊二烯负离子：共振与平衡边缘的Hückel芳香物种

Ankur 1, Bernd Morgenstern2, David Scheschkewitz1* Aromatic rings such as the ubiquitous π- ligand cyclopentadienide (C5H5−) adhere to the famous Hückel rule with their 4n+2 π cyclically delocalized electrons. Since the advent of stable Si–Si π- bonds in 1981, all- silicon aromatics have been targeted, yet only a three- membered cyclopropenium analog (Si3r3+; r, silyl) has been experimentally realized. We report a stable persilacyclopentadienide (Si5r5−; r, aryl), which is essentially planar and decidedly aromatic, although experimental and com putational data suggest an ultrarapid equilibrium between nonplanar isomers. With trimethylchlorostannane, Si5r5− rearranges the Si5 core to a tricyclic isomer confirming the pivotal role of the lithium cation for stability. The persilacyclopentadienide promises a rich chemistry akin to carbon- based cyclo pentadienides. …