title: Inverted Carbon Geometries: Challenges to Experiment and Theory.
abstract: Disproving a long C-C-bond textbook example: The reported 1.643 Å C-C bond in 5-cyano-1,3-dehydroadamantane was redetermined and "only" amounts to 1.584 Å. While this value is well reproduced with ab initio methods, some common DFT approaches perform poorly and are only consistent with CCSD(T)/cc-pVTZ optimizations for noninverted carbons. Large deviations from experiment were also found for other molecules with atypical electron density distributions, e.g., cubane, bicyclo[2.2.0]hexane, and bicyclo[2.1.0]- and bicyclo[1.1.1]pentane, thereby presenting challenging structures for some DFT implementations.
authors.affiliation: ⊥Merck KGaA Frankfurter Str. 250, 64293 Darmstadt, Germany.|§Institute of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Gemany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Bremer
authors.affiliation: ⊥Merck KGaA Frankfurter Str. 250, 64293 Darmstadt, Germany.
authors.forename: Harald
authors.initials: H
authors.lastname: Untenecker
authors.affiliation: ‡Department of Organic Chemistry, Kiev Polytechnic Institute, Pr. Pobedy 37, 03056 Kiev, Ukraine.
authors.forename: Pavel A
authors.initials: PA
authors.lastname: Gunchenko
authors.affiliation: ‡Department of Organic Chemistry, Kiev Polytechnic Institute, Pr. Pobedy 37, 03056 Kiev, Ukraine.
authors.forename: Andrey A
authors.initials: AA
authors.lastname: Fokin
authors.affiliation: §Institute of Organic Chemistry, Justus-Liebig University, Heinrich-Buff-Ring 58, 35392 Giessen, Gemany.
authors.forename: Peter R
authors.initials: PR
authors.lastname: Schreiner