Borinium, Borenium, and Boronium Ions: Synthesis, Reactivity, and Applications

Abstract

Boron cations are elusive and highly electrophilic species that play a key role in the chemistry of boron. Despite early interest in the chemistry of boron cations, until recently they have largely remained chemical curiosities. However, hints at harnessing their potential as potent electrophiles have begun to appear and developments in weakly coordinating anion technology suggest that this is an area of research that is ripe for exploration. It has been nearly 20 years since the last major review on boron cations; herein we summarize the progress in the area since that time.

Synthesis and structure of the coordinatively unsaturated boron subphthalocyanine cation, [B(SubPc)]+

“…Competition between coordinating anions and neutral N-atom donors has been studied in dialkylboreniumlike species, R 2 BL(SO 3 CF 3 ) [12]. The long-term goal of this work is to develop new Lewis acids based on borenium ions [13,14]. Boron subpthalocyanines are of current interest in the development of photoand electro-active assemblies [15], and axial ligand changes may become an important part of the finetuning of their electronic properties.…”

A Stable but Highly Reactive Phosphine‐Coordinated Borenium: Metal‐free Dihydrogen Activation and Alkyne 1,2‐Carboboration

“…L) + are valuable analogues of boranes. [3] Intra-and intermolecularly stabilized boreniums have been developed and the nature of the Lewis base has been modified to include pyridines, amines, N-heterocyclic carbenes (NHC), N-heterocyclic carbene olefins (NHO), carbodiphosphoranes, and phosphines. [4][5][6] Accordingly, the variety of stable boreniums has been considerably extended and our understanding of their electronic structure has progressed significantly.…”

Lewis Superacidic Ionic Liquids with Tricoordinate Borenium Cations

“…The most important routes to generate borenium cations are hydride or halide abstraction from tetracoordinate boron adducts, [BX3L], using an excess of abstracting agent (Figure 1). [4,5,7,10] Many borenium complexes have been reported as 'oily materials'. [4] Despite the increasing number of known crystal structures, [5,8,9] they are generally difficult to crystallize, and are typically studied in solution, using 11 B NMR spectroscopy.…”