Reduction of π‐Expanded Cyclooctatetraene with Lithium: Stabilization of the Tetra‐Anion through Internal Li⁺ Coordination

Abstract

Supporting information for this article is given via a link at the end of the document.

Reversible structural rearrangement of π-expanded cyclooctatetraene upon two-fold reduction with alkali metals

“…In summary, the controlled chemical reduction of large and contorted OPTBCOT ( 1 ) with different alkali metals in the presence of secondary ligands has been investigated. In contrast to the previously reported tetra-reduced product of 1 , 21 the uptake of two electrons is accompanied by an unusual transformation of the negatively charged core, which has been confirmed by X-ray crystallography. Notably, the new dianion with a more twisted COT moiety has been formed rather than the expected planarized aromatic core.…”

“…The chemical reduction of 1 with Li or Na metal in the presence of [2.2.2]cryptand and 18-crown-6 ether (Scheme 2) is accompanied by a pronounced color change and proceeds through two steps, which is different compared to the reduction observed in THF only. 21 The reaction solution color quickly turns blue followed by purple (483 and 576 nm) which is indicative of the formation of doubly-reduced product according to the UV-vis spectroscopy (Fig. S1–S4, ESI†).…”

“…Remarkably, reaction of 1 with excess lithium metal afforded a coordinatively stabilized tetraanion instead of the planarized aromatic dianion. 21…”

Redox‐Active Hydrocarbons: Isolation and Structural Determination of Cationic States toward Advanced Response Systems

“…In this review, we focus on examples of succeeding in isolation and structural determination of cationic species based on pure hydrocarbons with aromatic rings and introduce the intrinsic electrochemical and spectroscopic properties of such hydrocarbons. The X‐ray analysis of anionic species consisting of pure hydrocarbons has been achieved only recently [36–44] . Since only a few examples of reversible redox response systems are available, they are not considered in this review.…”

“…The X-ray analysis of anionic species consisting of pure hydrocarbons has been achieved only recently. [36][37][38][39][40][41][42][43][44] Since only a few examples of reversible redox response systems are available, they are not considered in this review. Heteroatom-containing hydrocarbons are also excluded from this review because the effect of the introduction of heteroatoms on the redox properties has been well-investigated and reported in several papers.…”