摘要 : In solution in acetone at room temperature, tris(perfluoropropanoyl and perfluorobutanoyl)benzoylmethanatecomplexes of rhodium(III) are shown by ~19F NMR spectroscopyto exist as nearly statistical 1:3 mixtures of their respective ... 展开 In solution in acetone at room temperature, tris(perfluoropropanoyl and perfluorobutanoyl)benzoylmethanatecomplexes of rhodium(III) are shown by ~19F NMR spectroscopyto exist as nearly statistical 1:3 mixtures of their respective fac andmer octahedral isomers, whereas the analogousperfluoroalkanoylthiobenzoylmethanate complexes have a fac-octahedral structure. For all four complexes studied, vicinal F-Fcoupling constants are too small (0-3 Hz) to lead to resolvedmultiplet peaks, so that perfluoroethyl groups show singletresonances for their CF_3 groups. Since four-bond couplingconstants are significantly larger, ~ Hz, peffluoropropyl groupsshow the expected multiplet resonances for their CF-3 groups. Inacetone, AB patterns, with geminal coupling constants equal to270 Hz, are observed for the CF-2 groups next to the chelate ring(except for the perfluoropropanoylthiobenzoylmethanate complex).(These observations are modified by solvent. In toluene, one of theAB patterns of a mer-octahedral complex collapses to a singlepeak.) The AB spectra, which are subject to substituent and solventeffects, can be interpreted in terms of perfluoroalkyl groupsrotating rapidly about the C_ing – C_alkyl bond, with anunsymmetric double potential well, giving unequal rotamerpopulations. changes in the spectra were not noticeable over thetemperature range accessible in the acetone and toluene solvents used. 收起