title: A Frustrated and Confused Lewis Pair.
abstract: We report a new class of frustrated Lewis pairs (FLPs) by the hydroboration of bulky isocyanatesiPr2ArNCO (iPr2Ar=2,6-iPr2C6H3) andPh2tBuArNCO (Ph2tBuAr=2,6-Ph2-4-tBuC6H2) with Piers' borane (HB(C6F5)2). While hydroboration of smaller isocyanates such asiPr2ArNCO leads to isocyanate-N/B FLP adducts, hydroboration of the bulkierPh2tBuArNCO 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.
authors.affiliation: Department of Chemistry, Georgetown University, Box 571227, Washington, DC, 20057-1227, USA.
authors.forename: Alison C
authors.initials: AC
authors.lastname: McQuilken
authors.affiliation: Mulliken Center for Theoretical Chemistry, Institut für Physikalische Chemie und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Deutschland.
authors.forename: Quang Minh
authors.initials: QM
authors.lastname: Dao
authors.affiliation: Department of Chemistry, Georgetown University, Box 571227, Washington, DC, 20057-1227, USA.|Department of Chemistry, State University of New York at Fredonia, 221 Science Center, Fredonia, NY, 14064, USA.
authors.forename: Allan Jay P
authors.initials: AJ
authors.lastname: Cardenas
authors.affiliation: Department of Chemistry, Georgetown University, Box 571227, Washington, DC, 20057-1227, USA.
authors.forename: Jeffery A
authors.initials: JA
authors.lastname: Bertke
authors.affiliation: Mulliken Center for Theoretical Chemistry, Institut für Physikalische Chemie und Theoretische Chemie, Universität Bonn, Beringstraße 4, 53115, Bonn, Deutschland. grimme@thch.uni-bonn.de.
authors.forename: Stefan
authors.initials: S
authors.lastname: Grimme
authors.affiliation: Department of Chemistry, Georgetown University, Box 571227, Washington, DC, 20057-1227, USA. thw@georgetown.edu.
authors.forename: Timothy H
authors.identifier: 0000-0001-9217-8890
authors.initials: TH
authors.lastname: Warren
keywords: acid-base interactions; density functional calculations; frustrated Lewis pairs; hydroboration; sustainable chemistry