Observation and interpretation of an unusual electric field gradient property in SbCl 3 · C 6H 5NH 2

Abstract

The 121Sb, 123Sb, and 35Cl nuclear quadrupole resonance spectrum of the antimony trichloride-aniline ( 1 1 ) complex is reported. The coupling constants for 123Sb and 123Sb are respectively 326.2 and 416.1 MHz and the asymmetry parameter is 0.03 ± 0.008. This very small asymmetry parameter is surprising in light of the asymmetric environment of Sb revealed by the crystal structure. Point charge and tangential sphere-point charge model calculations were carried out on the complex and reveal the cause of the small asymmetry parameter to be a fortuitous balancing of the electric field gradient components from the external atoms as a result of their arrangement. Both models are completely consistent with small antimony asymmetry but suggest that small distortions from the structure could produce substantial field gradient asymmetry at antimony.