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‐Me(2)C(6)H(3); anth=C(14)H(10) (2−), thf=tetrahydrofuran) toward Brønsted acid [NEt(3)H][BPh(4)] and azobenzene is reported. While a stepwise protonation of 2‐anth‐Li with two equivalents of [NEt(3)H][BPh(4)] afforded the scandium cation [Sc{N(tBu)Xy}(2)(thf)(2)][BPh(4)] (3), reduction of azobenzene gave a thermolabile, anionic scandium reduced azobenzene complex [Li(thf)][Sc{N(tBu)Xy}(2)(η (2)‐PhNNPh)] (4), which slowly lost one of the anilide ligands to form the neutral scandium azobenzene complex dimer [Sc{N(tBu)Xy}(μ‐η (2):η (2)‐Ph(2)N(2))](2) (5). Exposure of 3 to CO(2) produced the scandium carbamate complex [Sc{κ(2)‐O(2)CN(tBu)(Xy)}(2)][BPh(4)] (6) as a result of CO(2) insertion into the Sc−N bonds. In an attempt to prepare scandium hydrides, the reaction of 3 with the hydride sources LiAlH(4) and Na[BEt(3)H] 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.