Antimony-121 Mössbauer spectroscopic study of bis(halogenoacetato)trimethylantimony derivatives

Abstract

Antimony-121 Mössbauer spectra of a number of bis(halogenoacetato)trimethylantimony complexes [Me₃Sb(OCOR′)₂] have been measured. The compounds are shown to have trigonal bipyramidal structures with essentially planar C₃Sb groups. Comparisons with ¹¹⁹Sn Mössbauer data for the related [Me₃SnOCOR′] derivatives reveal a number of linear correlations. The trends in isomer shift δ and quadrupole splitting e²qQ as R′ changes in the [Me₃Sb(OCOR′)₂] series are very different from those observed upon changing X in the series [Ph₃SbX₂](X = F, Cl, Br, I, etc.). In the former compounds differences in both δ and e²qQ are dominated by the effects of p electron withdrawal, whilst in the latter series there appear to be substantial changes in hybridization of the Sb bonding orbitals.