Abstract
Over the last decade there has been an explosion in the reactivity and applications of frustrated Lewis pair (FLP) chemistry. Despite this, the Lewis acids (LAs) in these transformations are often boranes, with heavier p-block elements receiving surprisingly little attention. The novel LA Bn3SnOTf (1) has been synthesized from simple, inexpensive starting materials and has been spectroscopically and structurally characterized. Subtle modulation of the electronics at the tin centre has led to an increase in its Lewis acidity in comparison with previously reported R3SnOTf LAs, and has facilitated low temperature hydrogen activation and imine hydrogenation. Deactivation pathways of the R3Sn+ LA core have also been investigated.This article is part of the themed issue ‘Frustrated Lewis pair chemistry’.
Highlights
Since the concept of ‘frustrated Lewis pairs’ (FLPs) was formalized a decade ago [1], there has been a rapid increase in interest and activity in this area of chemistry [2,3,4]
It is notable that earlier work by Manners and co-workers showed similar FLP systems based on nBu3SnOTf were unreactive towards H2, they were capable of dehydrogenating amine-boranes. We proposed that this resulted from an overly strong interaction between the less bulky R3Sn+ and TfO– moieties, which would result in significant quenching of the Lewis acidity at Sn [15]; this hypothesis drove us to pursue the synthesis of the more sterically encumbered yet electronically similar iPr analogue
Subtle modulation of the electronics at the Sn centre by incorporating benzyl instead of the more common alkyl ligands on the R3Sn core has allowed for a successful increase in R3SnOTf Lewis acidity, as evidenced by the comparison of AN values calculated from the Gutmann–Beckett spectroscopic method
Summary
Over the last decade there has been an explosion in the reactivity and applications of frustrated Lewis pair (FLP) chemistry. The Lewis acids (LAs) in these transformations are often boranes, with heavier p-block elements receiving surprisingly little attention. The novel LA Bn3SnOTf (1) has been synthesized from simple, inexpensive starting materials and has been spectroscopically and structurally characterized. Subtle modulation of the electronics at the tin centre has led to an increase in its Lewis acidity in comparison with previously reported R3SnOTf LAs, and has facilitated low temperature hydrogen activation and imine hydrogenation. Deactivation pathways of the R3Sn+ LA core have been investigated. This article is part of the themed issue ‘Frustrated Lewis pair chemistry’
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