Scandium Reduced Arene Complex: Protonation and Reaction with Azobenzene.

The reactivity of the reduced anthracene complex of scandium [Li(thf)3][Sc{N(tBu)Xy}2(anth)] (2‐anth‐Li) (Xy=3,5‐Me2C6H3; anth=C14H102−, thf=tetrahydrofuran) toward Brønsted acid [NEt3H][BPh4] and azobenzene is reported. While a stepwise protonation of 2‐anth‐Li with two equivalents of [NEt3H][BPh4] afforded the scandium cation [Sc{N(tBu)Xy}2(thf)2][BPh4] (3), reduction of azobenzene gave a thermolabile, anionic scandium reduced azobenzene complex [Li(thf)][Sc{N(tBu)Xy}2(η2‐PhNNPh)] (4), which slowly lost one of the anilide ligands to form the neutral scandium azobenzene complex dimer [Sc{N(tBu)Xy}(μ‐η2:η2‐Ph2N2)]2 (5). Exposure of 3 to CO2 produced the scandium carbamate complex [Sc{κ2‐O2CN(tBu)(Xy)}2][BPh4] (6) as a result of CO2 insertion into the Sc−N bonds. In an attempt to prepare scandium hydrides, the reaction of 3 with the hydride sources LiAlH4 and Na[BEt3H] led to the terminal aluminum hydride [AlH{N(tBu)Xy}2(thf)] (7) and the scandium n‐butoxide [Sc{N(tBu)(Xy)}2(μ‐OnBu)] (8) after Sc/Al transmetalation and nucleophilic ring‐opening of THF, respectively. All reported compounds isolated in moderate to good yields were fully characterized. [ABSTRACT FROM AUTHOR]