Frustrated Lewis Pair Chelation and Reactivity of Complexed Parent Iminoborane and Aminoborane
Alvaro A. Omaña, Ryan Watt, Yuqiao Zhou, Michael J. Ferguson, Eric Rivard
Abstract
An intramolecular phosphine–borane frustrated Lewis pair (FLP) chelate, iPr2P(C6H4)BCy2 or PB (Cy = cyclohexyl), was used to coordinate aminoborane (H2BNH2) and iminoborane (HBNH) units via donor–acceptor stabilization. Attempts to induce dehydrogenation from these B–N adducts with known metal catalysts (or pre-catalysts) have been unsuccessful thus far, and related observations were noted with an H2BNH2 complex supported by a modified FLP chelate bearing a geometrically constrained bicyclic 9-borabicyclo(3.3.1)nonane (BBN) unit. Treatment of the iminoborane adduct [PB{HBNH}] with a chlorinating agent led to ligand activation via B–C bond cleavage instead of the expected H/Cl exchange at boron to give [PB{ClBNH}]. Nucleophilic attack at the boron center in [PB{HBNH}] was observed upon addition of BnK (Bn = benzyl), yielding the amidoborate complex [PB{H(Bn)BNH}{K(THF)2}].