Mononuclear gallium complexes with the redox-active dmp-bian ligand (dmp-bian is 1,2-bis[(2,6-dimethylphenyl)imino]acenaphthene): synthesis and reactions with alkynes

The direct reduction of 1,2-bis[(2,6-dimethylphenyl)imino]acenaphthene (dmp-bian (1)) with gallium metal in toluene affords the solvent-free bis-ligand complex [(dmp-bian)2Ga] (2), in which two diimine ligands are in different oxidation states (radical-anionic and dianionic). The addition of phenylacethylene to the Ga–N–C moiety of the dianionic ligand of compound 2 gives the complex [(dmp-bian)Ga(HC=CPh)(dmp-bian)] (3), in which new Ga–C and C–C bonds are formed. The reaction of 2 with hex-1-yne produces the gallium dialkynyl complex [(dmp-bian)Ga(C≡C–Bu)2] (4), with the metal atom bonded to the dmp-bian radical anion. Paramagnetic compounds 2–4 were characterized by ESR spectroscopy and X-ray diffraction. The known compound dmp-bian was structurally characterized for the first time.