A Frustrated and Confused Lewis Pair

Alison C McQuilken; Quang Minh Dao; Allan Jay P Cardenas; Jeffery A Bertke; Stefan Grimme; Timothy H Warren

doi:10.1002/anie.201608968

A Frustrated and Confused Lewis Pair

Angew Chem Int Ed Engl. 2016 Nov 7;55(46):14335-14339. doi: 10.1002/anie.201608968. Epub 2016 Oct 13.

Authors

Alison C McQuilken¹, Quang Minh Dao², Allan Jay P Cardenas^{1

3}, Jeffery A Bertke¹, Stefan Grimme⁴, Timothy H Warren⁵

Affiliations

¹ Department of Chemistry, Georgetown University, Box 571227, Washington, DC, 20057-1227, USA.
² Mulliken Center for Theoretical Chemistry, Institut für Physikalische Chemie und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Deutschland.
³ Department of Chemistry, State University of New York at Fredonia, 221 Science Center, Fredonia, NY, 14064, USA.
⁴ Mulliken Center for Theoretical Chemistry, Institut für Physikalische Chemie und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Deutschland. grimme@thch.uni-bonn.de.
⁵ Department of Chemistry, Georgetown University, Box 571227, Washington, DC, 20057-1227, USA. thw@georgetown.edu.

PMID: 27735119
DOI: 10.1002/anie.201608968

Abstract

We report a new class of frustrated Lewis pairs (FLPs) by the hydroboration of bulky isocyanates ^iPr2 ArNCO (^iPr2 Ar=2,6-iPr₂ C₆ H₃ ) and ^Ph2tBu ArNCO (^Ph2tBu Ar=2,6-Ph₂ -4-tBuC₆ H₂ ) with Piers' borane (HB(C₆ F₅ )₂ ). While hydroboration of smaller isocyanates such as ^iPr2 ArNCO leads to isocyanate-N/B FLP adducts, hydroboration of the bulkier ^Ph2tBu ArNCO allows isolation of the substrate-free aminoborane with a short, covalent N-B bond. This confused FLP reversibly binds unsaturated substrates such as isocyanates and isocyanides, suggesting the intermediacy of a "normal" FLP along the reaction pathway, supported by high-level DFT studies and variable-temperature NMR spectroscopy. These results underscore the possibility of FLP behavior in systems that possess no obvious frustrated Lewis acid-base interaction.

Keywords: acid-base interactions; density functional calculations; frustrated Lewis pairs; hydroboration; sustainable chemistry.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.
Research Support, Non-U.S. Gov't