Pnictogen^III Dications Supported by BZIMPY Ligands

Two homologous series of pnictogen(III) dications, stabilized by 2,6-bis(benzimidazole-2-yl)pyridine ligands have been prepared. Both series contain Pn^III-X moieties (Pn = P, As, Sb, Bi; X = Cl or Ph) and have been fully characterized using spectroscopic methods including X-ray crystallography. The Lewis acidity of these compounds has also been probed by computational methods; the results suggest that the dictations are strong Lewis acids, with the PnCl²⁺ compounds being more acidic than the PnPh²⁺ compounds, and with Lewis acidity increasing from P to Bi, in both series. The PhP²⁺-containing compound was also found to be a versatile P^III transfer reagent, leading to new synthetic routes for various PhP-containing compounds. The redox chemistry of all compounds has also been probed using cyclic voltammetry and chemical reductions. In some cases the resulting Pn^I moieties could be trapped using diazabutadienes.