Dehydrogenative Dual Ammonia Activation and Transfer by an N-Heterocyclic Boryloxy Aluminyl Compound

Abstract

The reactivity of an N-heterocyclic boryloxy (NHBO) ligated aluminyl compound has been harnessed for main-group-mediated dehydrogenative dual activation of ammonia. The Al(I) system K[{(HCDippN)2BO}2Al] reacts with excess NH3 to give the Al(III) bis(amide) K[{(HCDippN)2BO}2Al(NH2)2] and in the process generates H2. The initial stage of the reaction proceeds via formal N−H oxidative addition at Al(I) (via a coordination/proton shuttling sequence) to give an aluminium(III) primary amido hydride. Subsequent protonolysis of the strongly hydridic Al−H bond selectively yields the corresponding aluminium bis(amide) and H2. This step occurs without competing protolytic ligand loss – exploiting the limited basicity of the supporting [(boryl)O]− donors. In terms of amide transfer reactivity, the utility of K[{(HCDippN)2BO}2Al(NH2)2] in delivering one or both equivalents of [NH2]− to electrophilic substrates (HBpin, CO2 and Ph2CO) has been demonstrated.