Electric-field effects in nuclear magnetic resonance spectroscopy. Part III. 13C–1H spin–spin coupling constants
Abstract
If the linear electric-field dependence of the 13C–1H spin–spin coupling constants in polar acetylacetonato-complexes is assumed to depend on the different electric field at both the 13C and 1H nucleus, then effects at 1H are shown to be predominant. Previous empirical equations giving the quantitative dependence of the coupling constant on electric field are revised, and shown to be consistent with theory. When electric-field effects are important, there is also a linear relationship between the 1H and 13C shifts and the corresponding 13C–1H coupling constant for both the methyl and methine groups.