Fig. 4: Formation of a heteroleptic sandwich.
From: The anti-aromatic dianion and aromatic tetraanion of [18]annulene
a, Observed conformation of 14− and the corannulene tetraanion 24−. b,c, 1H NMR spectra of 12·Li8 (b) and 1·2·Li8 (c) (500 MHz, THF-d8, 25 °C; * denotes a trace of benzene). d, 7Li NMR spectrum of 1·2·Li8 (194 MHz, THF-d8, −80 °C). e, The single-crystal X-ray structure of 1·2·Li8 with minor disorder components and hydrogen atoms omitted for clarity and with C–Li distances in the range 2.180(15)–2.694(16) Å indicated by thin tubes. f,g, Two orthogonal views of the sandwich unit: top view (f) and side view (g). Colour code: C, grey; O, red; Li, blue.
