Donor–Acceptor Complexation and Dehydrogenation Chemistry of Aminoboranes

A series of formal donor–acceptor adducts of aminoborane
(H2BNH2) and its N-substituted analogues (H2BNRR′) were prepared: LB-H2BNRR′2-BH3 (LB = DMAP, IPr, IPrCH2 and PCy3; R and R′ = H, Me or tBu; IPr = [(HCNDipp)2C:] and Dipp = 2,6-iPr2C6H3). To potentially access complexes of molecular boron
nitride, LB-BN-LA (LA = Lewis acid), preliminary dehydrogenation chemistry
involving the parent aminoborane adducts LB-H2BNH2-BH3 was investigated using [Rh­(COD)­Cl]2, CuBr,
and NiBr2 as dehydrogenation catalysts. In place of isolating
the intended dehydrogenated BN donor–acceptor complexes, the
formation of borazine was noted as a major product. Attempts to prepare
the fluoroarylborane-capped aminoborane complexes, LB-H2BNH2-B­(C6F5)3, are also
described.