Bonding studies of compounds of boron and the group IV elements. Part IV. Redistribution equilibria among the boron trihalides by 11B nuclear resonance

Abstract

Redistribution equilibria: ⅔BX₃+⅓BY₃⇌ BX₂Y and ⅓BX₃+⅔BY₃⇌ BXY₂ among all the boron trihalides have been examined by ¹¹B n.m.r. spectroscopy in solvents methylcyclohexane and 1,1-dichloroethane at 33·5 °C; variable temperature studies have been completed for the BCl₃–BBr₃ systems. Entropy changes were also calculated from spectroscopic data and show tittle deviation from calculations based on symmetry factors alone. The reactions depart only slightly from thermoneutrality (<2 kcal mol^–1) and endothermicity appears to increase with increasing disparity between the electronegativities of X and Y. There is no detectable solvent effect in the two media examined and, insofar as comparison permits, no significant deviation from the situation in the gas phase.