Consequence of Ligand Bite Angle on Bismuth Lewis Acidity.

Ligand bite angle, a common parameter to fine-tune reactivity in transition-metal chemistry, is used for the first time in main-group chemistry to control and tune the Lewis acidity in organobismuth cations bearing 2-[(dimethylamino)methyl]phenyl (MeNCHCH) and 2-(dimethylamino)phenyl (MeNCH) ligands. The latter chelating ligand induces a shorter C-Bi-N bite angle, leading to a weaker Bi-N bond with a corresponding lower Bi-N σ*-acceptor orbital and hence exhibiting remarkably higher Lewis acidity. The Gutmann-Beckett method is successfully employed to quantify the Lewis acidity in organobismuth cations.