The Synthesis Properties and Reactivity of Lewis Acidic Aminoboranes

Abstract

<div> <p>The evolution of frustrated Lewis pair chemistry has led to significant research into the development of new Lewis acidic boranes. Much of this has focused on modifying aryl substituents rather than introducing heteroatoms bound to boron. We recently reported unique Lewis acidic behaviour from bis(pentafluorophenyl)phenothiazylborane (<b>1</b>) for the heterolytic dehydrocoupling of stannanes. In this work, we synthesize and characterize a family of Lewis acidic aminoboranes and explored their reactivity with various Lewis bases as well as their efficacy as catalysts for stannane dehydrocoupling and hydrosilylation. Quantum chemical caluclations were undertaken to understand the origins of the Lewis acidity and the most Lewis acidic aminoborane (<b>5</b>) was found to be an effective catalyst even in coordinating solvents such as water or acetonitrile, suggesting the amino substituent provides a level of protection against competing donors. </p> </div> <br>

Interrogating Redox and Lewis Base Activations of Aminoboranes

“…17 Thus, a fundamental study elucidating the reactivity properties of aminoboranes will provide critical knowledge needed to advance this field. 18 Figure 2. Are neutral Lewis bases (left) and/or electro-/photochemical methods (right) capable of effecting aminoborane activation?…”

Interrogating Redox and Lewis Base Activations of Aminoboranes

“…18 Therefore, a fundamental study of the reactivity properties of aminoboranes will provide critical knowledge needed to advance this field. 19 We hypothesized that coordination of a neutral Lewis base to boron or one-electron oxidation of the nitrogen atom could sufficiently diminish, if not obviate, the impact of the B=N resonance contributor and furnish activated aminoboranes (Figure 2). 20 Herein, we show that super-stoichiometric quantities of neutral Lewis bases give rise to aminoborane/neutral Lewis base adducts lying thermodynamically uphill from the aminoborane and neutral Lewis base components, thus significantly disfavoring their formation using catalytic quantities of neutral Lewis base.…”