JEFFREY M. FARRELLStephan, Douglas W.Douglas W.Stephan2022-05-272022-05-272015https://www.scopus.com/inward/record.uri?eid=2-s2.0-85027928783&doi=10.1002%2fanie.201500198&partnerID=40&md5=2dfbdb811413c152b1c495b6eab1c87chttps://scholars.lib.ntu.edu.tw/handle/123456789/612095The NHC-borane adduct (IBn)BH3 (1) (NHC= N-heterocyclic carbene; IBn=1,3-dibenzylimidazol-2ylidene) reacts with [Ph3C][B(C6F5)4] through sequential hydride abstraction and dehydrogenative cationic borylation(s) to give singly or doubly ring closed NHC-borenium salts 2 and 3. The planar doubly ring closed product [C3H2(NCH2C6H4)2B][B(C6F5)4] is resistant to quaternization at boron by Et2O coordination, but forms classical Lewis acid-base adducts with the stronger donors Ph3P, Et3PO, or 1,4-diazabicyclo[2.2.2]octane (DABCO). Treatment of 3 with tBu3P selectively yields the unusual oligomeric borenium salt trans-[(C3H2(NCH2C6H4)2B)2(C3H2(NCHC6H4)2B)][B(C6F5)4] (7). Boron in action: Singly or doubly ring closed NHC-borenium salts (NHC= N-heterocyclic carbene) are prepared by dehydrogenative cationic borylation. Treatment of the planar doubly ring closed product (see picture, left) with tBu3P leads to the formation of an unusual trans C2-symmetric oligomeric borenium salt (right). Atom colors: C, black; N, blue; B, yellow. ? 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.boranes; borylation; carbenes; frustrated Lewis pairs; steric hindranceBoron; Hydrides; Oligomers; Salts; Synthesis (chemical); boranes; Borylation; Carbenes; Frustrated lewis pairs; Steric hindrances; Organic compoundsjournal article10.1002/anie.2015001982-s2.0-85027928783