Abstract
The Lewis acidity of tris(ortho-carboranyl)borane has been slightly increased by mimicking the structural evolution from triarylborane to 9-aryl-9-borafluorene. The o-carborane-based analogue (C(2)B(10)H(10))(2)B(C(2)B(10)H(11)), obtained via salt elimination between LiC(2)B(10)H(11) and (C(2)B(10)H(10))(2)BBr, has been fully characterized. Gutmann-Beckett and computational fluoride/hydride ion affinity (FIA/HIA) studies have confirmed the increase in Lewis acidity, which is attributable to structural constraint imposed by the CC-coupling between two carboranyl groups. Selective complexation of (C(2)B(10)H(10))(2)B(C(2)B(10)H(11)) with Bestmann ylides R(3)PCCO (R = Ph, Cy) has been achieved, enabling further conversion into the zwitterionic phospholium salt through NHC-catalyzed proton transfer.