Redox‐Active Ligand‐Assisted Two‐Electron Oxidative Addition to Gallium(II)

The reaction of digallane (dpp‐bian)Ga−Ga(dpp‐bian) ( 2 ) (dpp‐bian=1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene) with allyl chloride (AllCl) proceeded by a two‐electron oxidative addition to afford paramagnetic complexes (dpp‐bian)Ga(η 1 ‐All)Cl ( 3 ) and (dpp‐bian)(Cl)Ga−Ga(Cl)(dpp‐bian) ( 4 ). Treatment of complex 4 with pyridine induced an intramolecular redox process, which resulted in the diamagnetic complex (dpp‐bian)Ga(Py)Cl ( 5 ). In reaction with allyl bromide, complex 2 gave metal‐ and ligand‐centered addition products (dpp‐bian)Ga(η 1 ‐All)Br ( 6 ) and (dpp‐bian‐All)(Br)Ga−Ga(Br)(dpp‐bian‐All) ( 7 ). The reaction of digallane 2 with Ph 3 SnNCO afforded (dpp‐bian)Ga(SnPh 3 ) 2 ( 8 ) and (dpp‐bian)(NCO)Ga−Ga(NCO)(dpp‐bian) ( 9 ). Treatment of GaCl 3 with (dpp‐bian)Na in diethyl ether resulted in the formation of (dpp‐bian)GaCl 2 ( 10 ). Diorganylgallium derivatives (dpp‐bian)GaR 2 (R=Ph, 11 ; t Bu, 14 ; Me, 15 ; Bn, 16 ) and (dpp‐bian)Ga(η 1 ‐All)R (R= n Bu, 12 ; Cp, 13 ) were synthesized from complexes 3 , 10 , Bn 2 GaCl, or t Bu 2 GaCl by salt metathesis. The salt elimination reaction between (dpp‐bian)GaI 2 ( 17 ) and t BuLi was accompanied by reduction of both the metal and the dpp‐bian ligand, which resulted in digallane 2 as the final product. Similarly, the reaction of complex 10 with MentMgCl (Ment=menthyl) proceeded with reduction of the dpp‐bian ligand to give the diamagnetic complex [(dpp‐bian)GaCl 2 ][Mg 2 Cl 3 (THF) 6 ] ( 18 ). Compounds 11 , 12 , 13 , 15 , and 16 were thermally robust, whereas compound 14 decomposed when heated at reflux in toluene to give complex (dpp‐bian‐ t Bu)Ga t Bu 2 ( 19 ). Both complexes 7 and 19 contain R‐substituted dpp‐bian ligand: in the former compound the allyl group was attached to the imino‐carbon atom, whereas in complex 19 , the t Bu group was situated on the naphthalene ring. Crystal structures of complexes 3 , 8 , 9 , 10 , 13 , 14 , 18 , and 19 were determined by single‐crystal X‐ray analysis. The presence of dpp‐bian radical anions in 3 , 6 , 8 , and 10 – 16 was determined by ESR spectroscopy.