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

Abstract

Attempted coordination of "Ga(I)I" with two new sterically bulky, aryl substituted bis(imino)pyridine ligands lead to Ga(III) species [2,6-{ArN=CPh}(2)(NC(5)H(3))]GaI(2)(+)GaI(4)(-) (Ar = 2,5-(t)Bu(2)C(6)H(3), 2,6-(i)Pr(2)C(6)H(3) = Dipp) arising from thermodynamically favorable disproportionation reactions. Examination of these reactions lead to isolation of a neutral radical species [2,6-{DippN=CPh}(2)(NC(5)H(3))]GaI(2). Both EPR spectroscopy and DFT calculations on this compound indicate that the unpaired electron is localized in a di(imino)pyridine pi* orbital of an anionic ligand with nearly zero contribution from the Ga or I centers. Reaction of {2,5-(t)Bu(2)C(6)H(3)N=CPh}(2)(NC(5)H(3)) with AlCl(3) yielded an analogous Al(iii) product, [{2,5-(t)Bu(2)C(6)H(3)N=CPh}(2)(NC(5)H(3))]AlCl(2)(+)AlCl(4)(-).