Bonding studies of compounds of boron and the Group 3–5 elements. Part XIV. Redistribution equilibria in phenylboron dihalide and boron trihalide systems

Abstract

Redistribution reactions for two sets of trigonal boron systems, (i) PhBX₂–PhBY₂ and (ii)PhBX₂–BY₃, have been investigated, principally by ¹¹B n.m.r. spectroscopy for samples in sealed tubes. For (i) when X = F and Y = Cl or Br, equilibrium constants at 316·5 K have been obtained, and small ΔH^⊖ values and close to statistical ΔS^⊖ for the former have been derived from second-law plots. For (ii), PhBF₂ and BCl₃ or BBr₃ give quantitative transformation into PhBCl₂ or PhBBr₂ and BF₃ at 316·5 K. From these and literature data, standard heats of reactions are derived for various systems related to (i) and (ii).