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.