2,6-Bis(diazaboryl)pyridine: A superbasic sterically demanding pyridine ligand

Abstract: Herein we present a convenient one-pot route to a sterically demanding superbasic pyridine. Functionalization of the 2,6-positions with the highly sigma-donating boryl-groups shifts the calculated gas phase basicity of the pyridine's nitrogen atom to 1012 kJ mol-1, which outperforms the 'proton sponge' 1,8-bis(dimethylamino)naphthalene (996 kJ mol-1). The diazaboryl groups are oriented orthogonal to the pyridine ring and do not block the N-position, resembling the geometry of commonly used N-heterocyclic carbenes. This allows for its application as a neutral N-donor ligand in coordination chemistry, as demonstrated here with the Lewis acid/base adducts of haloboranes. With this new ligand, we hope to provide a weaker coordinating alternative to NHCs, which sometimes form extraordinary stable adducts and do not allow ligand free further chemistry.