Synthesis and structures of mononuclear and dinuclear gallium complexes with α-diimine ligands: reduction of the metal or ligand?

Abstract

Reduction of the dichloro gallium(III) α-diimine complex [(L^ipr)˙⁻GaCl₂] (1, L^ipr = [(2,6-iPr₂C₆H₃)NC(Me)]₂) by different equivalents of sodium metal afforded the gallium complexes [(L^ipr)²⁻Ga^III(μ₂-Cl)₂Na(THF)₄] (2) and [(Na(THF)₆)⁺·((L^ipr)²⁻Ga–Ga(L^ipr)²⁻)˙⁻] (3). Interestingly, in complex 2 a Na⁺Cl⁻ ion pair is incorporated, while compound 3 is an anionic digallium complex. Moreover, a cationic gallium complex with a tetrachlorogallium(III) counter anion, [(LGaCl₂)⁺·(GaCl₄)⁻] (4), was accessed from the reaction of GaCl₃ with 0.5 equiv. of ligand L^ipr. In contrast, the reaction of GaCl₃ with the doubly reduced anion (Na₂L²⁻) of the smaller α-diimine ligands L^Me ([(2,6-Me₂C₆H₃)NC(Me)]₂) or L^Et ([(2,6-Et₂C₆H₃)NC(Me)]₂) yielded the Ga–Ga-bonded complexes [(L^Et)˙⁻ClGa^II–Ga^IICl(L^Et)˙⁻] (5) and [(L^Me)˙⁻ClGa^II–Ga^IICl(L^Me)˙⁻] (6). Here L is the neutral α-diimine ligand, L˙⁻ represents the monoanion, and L²⁻ is the dianionic form of the ligand. The complexes were characterized by X-ray diffraction and their electronic structures were studied by DFT computations.