Variable-Temperature F NMR and Theoretical Study of 1,9- and 1 ,7-CF(CF) and C and C-CF(CF): Hindered CF Rotation and Through-Space J Coupling.
Milligram amounts of the new compounds 1,9- and 1,7-CF(CF) (Ca. 85:15 mixture of isomers) and CF(CF) were isolated from a high-temperature C/KPtF reaction mixture and purified to 98 mol % compositional purity by two-dimensional high-performance liquid chromatography using Buckyprep and Buckyclutcher...
| Published in: | Journal of the American Chemical Society Vol. 127; no. 32; pp. 11497 - 11505 |
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| Main Authors: | , , , , , , , , , |
| Format: | Article |
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American Chemical Society
8/17/2005
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| Subjects: | |
| Online Access: | View this record in EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=18026753&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 18026753 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 8/17/2005 vid: 127 iid: 32 pid: 997 pub: American Chemical Society artinfo: ui: 18026753 10.1021/ja051954y ppf: 11497 ppct: 8 formats: tig: atl: Variable-Temperature F NMR and Theoretical Study of 1,9- and 1 ,7-CF(CF) and C and C-CF(CF): Hindered CF Rotation and Through-Space J Coupling. aug: au: Kareev, Ivan E. Quiñones, Gustavo Santiso Kuvycho, Igor V. Khavrel, Pavel A. Ioffe, Ilya N. Goldt, Ilya V. Lebedkin, Sergey F. Seppelt, Konrad Strauss, Steven H. Boltalina, Olga V. affil: Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka 142432 Russia. Forschungszentrum Karlsruhe, Institute for Nanotechnology, Karlsruhe 76021 Germany. Institut für Anorganische und Analytische Chemie der Freien Universität, Berlin D14195 Germany. Chemistry Department, Moscow State University, Moscow 119992 Russia. Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523. su: Nuclear magnetic resonance Temperature Spectrum analysis Density functionals Liquid chromatography Chemical reactions Research sug: subj: Nuclear magnetic resonance Temperature Spectrum analysis Density functionals Liquid chromatography Chemical reactions Research ab: Milligram amounts of the new compounds 1,9- and 1,7-CF(CF) (Ca. 85:15 mixture of isomers) and CF(CF) were isolated from a high-temperature C/KPtF reaction mixture and purified to 98 mol % compositional purity by two-dimensional high-performance liquid chromatography using Buckyprep and Buckyclutcher columns. The previously observed compounds CF(CF) and CF(CF) were also purified to 90+ mol % for the first time. Variable-temperature F NMR spectra of the mixture of CF(CF) isomers and the previously reported mixture of C and C-CF(CF) isomers demonstrate for the first time that fullerene(F)(CF) derivatives with adjacent F and CF substituents exhibit slow-exchange limit hindered CF rotation spectra at -40 ± 10 °C. The experimental and density functional theory (DFT) predicted ΔH‡ values for CF rotation in 1,9-CF(CF) are 46.8(7) and 46 kJ mol, respectively. The DFT-predicted ΔH‡ values for 1,7-CF(CF), CCF(CF), and C-CF(CF) are 20, 44, and 54 kJ mol, respectively. The J values from the slow-exchange-limit F spectra, which vary from ca. 0 to 48(1) Hz, show that the dominant nuclear spin-spin coupling mechanism is through-space coupling (i.e., direct overlap of fluorine atom lone-pair orbitals) rather than coupling through the σ-bond framework. The J values within the CF groups vary from 107(1) to 126(1) Hz. Collectively, the NMR data provide an unambiguous set of J values for three different compounds that can be correlated with DFT-predicted or X-ray diffraction derived distances and angles arid an unambiguous set of J values that can serve as an internal standard for all future J calculations. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2005 holdings: @attributes: islocal: N |
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