Silolyl Anions and Silole Dianions: Structure of [K([18]crown‐6)+]2[C4Me4Si2−]

Nearly equivalent CC distances in the five-membered ring of the dianion C4Me4Si2−, which could be isolated in crystalline form as a potassium salt in the presence of [18]crown-6 (structure on the right), suggest a high degree of delocalization. In contrast, 29Si and 13C NMR spectroscopic investigations of the silolyl anions C4Me4SiR− (R  SiMe3, Si(SiMe3)C4Me4) show that delocalization in these systems is minimal.