| Sumario: | 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.
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