Symmetric and asymmetric cleavage of the lighter boron hydrides and of metal salts – the role of the dielectric constant

Evidence is presented to support the premise that when a base reacts with diborane at low temperatures (−77 to −80°C) the variable which determines whether the product will be an ionic substance such as [H2B(Base)2]+[BH4−] or a non-ionic substance such as H3B(Base) is the dielectric constant of the base and the medium. In most cases steric factors do not play a dominant role in the outcome of these direct reactions.