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Structural and Electronic Effects of Stepwise Reduction of a Tetraaryl[3]Cumulene
Author(s) -
Spisak Sarah N.,
Bühringer Martina U.,
Wei Zheng,
Zhou Zheng,
Tykwinski Rik R.,
Petrukhina Marina A.
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201812283
Subject(s) - cumulene , chemistry , counterion , crystallography , metal , molecule , alkali metal , alkyne , ion , solvent , bond length , inorganic chemistry , photochemistry , crystal structure , organic chemistry , catalysis
The chemical reduction of a [3]cumulene ([3]TrTol) has been explored using alkali metals. Mono‐ and doubly reduced forms of [3]TrTol were isolated as solvent‐separated ion pairs with {Na(18‐crown‐6)THF 2 } + and {K(18‐crown‐6)THF 2 } + counterions and crystallographically characterized. This allowed analysis of structural parameters of the “naked” anions of [3]TrTol without interference from metal binding. The dianion of [3]TrTol was also isolated as a contact‐ion complex with {Cs(18‐crown‐6)} + cations, thereby adding the effect of metal coordination to the core. Structural comparisons of anions to the neutral molecule, [3]TrTol, outline monotonic increases in bond‐length alternation (BLA) upon stepwise reduction. The greatest BLA value is found for the contact‐ion complex, which shows an alternating sequence of short and long carbon–carbon bonds, consistent with the structure of an alkyne. In contrast to studies on tetraphenyl[3]cumulene, the cumulenic framework of [3]TrTol remains planar in all the derivatives.