Dialane with a Redox‐Active Bis‐amido Ligand: Unique Reactivity towards Alkynes

The treatment of 1,2‐bis[(2,6‐diisopropylphenyl)imino]acenaphthene (dpp‐bian) with one equivalent of AlCl 3 and three equivalents of sodium in toluene at 110 °C produced a stable dialane, (dpp‐bian)AlAl(dpp‐bian) ( 1 ). The reaction of compound  1 with pyridine gave Lewis‐acid–base adduct (dpp‐bian)(Py)AlAl(Py)(dpp‐bian) ( 2 ). Acetylene and phenylacetylene reacted with compound 1 to give cycloaddition products [dpp‐bian(R 1 R 2 )]AlAl[(R 2 R 1 )dpp‐bian] ( 3 : R 1 =R 2 =CH; 4 : R 1 =CH, R 2 =CPh). These addition reactions occur across Al‐N‐C moieties and result in the formation of new CC and CAl bonds. At elevated temperatures, compound 4 rearranges into complex 5 , which consists of a radical‐anionic dpp‐bian ligand and two bridging alken‐1,2‐diyl moieties, (dpp‐bian)Al(HCCPh) 2 Al(dpp‐bian). This transformation is accompanied by cleavage of the dpp‐bian‐ligand–alkyne CC bond, as well as of the AlAl bond. In contrast to its analogous gallium complex, compound 1 is reactive towards internal alkynes. In the reaction of compound 1 with PhCCMe, besides symmetrical addition product [dpp‐bian(R 1 R 2 )]AlAl[(R 2 R 1 )dpp‐bian] (R 1 =CMe, R 2 =CPh; 6 ), monoadduct [dpp‐bian(R 1 R 2 )]AlAl(dpp‐bian) (R 1 =CMe, R 2 =CPh; 7 ) was also isolated. Complexes 1 – 7 were characterized by IR, 1 H NMR ( 1 – 4 ), and electronic absorption spectroscopy ( 3 – 5 ); the molecular structures of compounds 1 – 7 were determined by single‐crystal X‐ray diffraction.