Correlations in 11B NMR spectra of dihalo derivatives of bis(1,2-dicarbollyl)cobalt(III)

Abstract

In the 11B NMR spectra of dihalo derivatives of bis(dicarbollyl)cobalt(III), we have identified a correlation between the 11B NMR chemical shifts of substituted boron atoms and boron atoms found in other positions on the carborane skeleton. We have observed an increased shielding effect for fluorine atoms (compared with other halogens), manifested in an upfield shift of the 11B NMR signals for antipodal and trans boron atoms. For the fluorine-containing compound Bu4N+ [8,8′-F2-3,3′-Co(1,2-C2B9H10)2]−, we propose the following sequence of electron density transfer: B(8) → {B(6) and B(10)} → B(4, 7).