Carbon-13 Nuclear Magnetic Resonance Spectra of Metal 2-Thenoyltrifluoroacetonates

Abstract

Carbon-13 NMR spectra of metal 2-thenoyltrifiuoroacetonates (M(TTA)., M=Mg, Ca, Sr, Ba, Zn, Cd, Pb, Al, Ga, ln) and 2-thenoyltrifluoroacetone (TTA) have been observed at 25.2 MHz. The resonance lines were assigned on basis of 1)the relative signal intensity, 2) the chemical shift and spin eoupling constant of homologous eompounds, 3) off-resonance decoupling techniq ue.
The values of iSC chemical shifts of TTA and M(TTA)n were given Table 1 and 3, respectiveiy.13C chemical shifts of C-1 and C-3 carbon on chelate ring in M(TTA)n had a correlation with electronegativity of metal bonded to the chelates. 13C resonance peak of C-1 and C-3 carbon shifted to lower magnetic field with increasing electronegativity as shewn in Fig.3. 13C chemical shifts of C-2 carbon on chelate ring was found tocorrelate with chemical shifts of proton bonded to C-2 carbon as shown in Fig. 7. 13C chemical shifts of C-2 carbon were also had a correlation withionic radius of the metal. 13C peak of C-2 carbon shifted to higher magnetic field with increasing ionic radius as shown in Fig. 6.
The coupling constants between carbon-13 and fiuorine were correlated with ionic radius or electronegativity of the metal. Coupling constant Ji3c-F increased with increasing ionic radius, while J13c c F decreased with increasing ionic radius as shown in Fig. 10.