Disproportionation and radical formation in the coordination of “GaI” with bis(imino)pyridines

Abstract

Attempted coordination of “Ga^II” with two new sterically bulky, aryl substituted bis(imino)pyridine ligands lead to Ga^III species [2,6-{ArNCPh}₂(NC₅H₃)]GaI₂⁺GaI₄⁻ (Ar = 2,5-^tBu₂C₆H₃, 2,6-ⁱPr₂C₆H₃ = Dipp) arising from thermodynamically favorable disproportionation reactions. Examination of these reactions lead to isolation of a neutral radical species [2,6-{DippNCPh}₂(NC₅H₃)]GaI₂. Both EPR spectroscopy and DFT calculations on this compound indicate that the unpaired electron is localized in a di(imino)pyridine π* orbital of an anionic ligand with nearly zero contribution from the Ga or I centers. Reaction of {2,5-^tBu₂C₆H₃NCPh}₂(NC₅H₃) with AlCl₃ yielded an analogous Al(III) product, [{2,5-^tBu₂C₆H₃NCPh}₂(NC₅H₃)]AlCl₂⁺AlCl₄⁻.