Heterolytic Cleavage of Dihydrogen by 'Frustrated Lewis Pairs' Comprising Bis(2,4,6-tris(trifluoromethyl)phenyl)borane and Amines: Stepwise versus Concerted Mechanism

摘要

Recently, the chemistry of "frustrated Lewis pairs" (FLPs), which was introduced by the research groups of Stephan and Erker, has received considerable attention. One of the most remarkable applications of FLPs is in the heterolytic activation of H2 without the involvement of transition-metals. A variety of FLP systems have been shown to activate H2 under mild conditions, and have been applied as catalysts in metal-free hydrogenation reactions.By analogy to the transition metal chemistry, it was originally proposed by Stephan and co-workers that the activation of H2 is a stepwise process, in which H2 is initially activated by the Lewis acid, followed by proton transfer to the Lewis base (Scheme 1).