Reduced Arene Complexes of Scandium

Alkali metal naphthalenide or anthracenide reacted with scandium(III) anilides [Sc(X){N(tBu)Xy}(2)(thf)] (X=N(tBu)Xy (1); X=Cl (2); Xy=C(6)H(3)‐3,5‐Me(2)) to give scandium complexes [M(thf)(n)][Sc{N(tBu)Xy}(2)(RA)] (M=Li–K; n=1–6; RA=C(10)H(8) (2−) (3‐Naph‐K) and C(14)H(10) (2−) (3‐Anth‐M)) containing a reduced arene ligand. Single‐crystal X‐ray diffraction revealed the scandium(III) center bonded to the naphthalene dianion in a σ(2):π‐coordination mode, whereas the anthracene dianion is symmetrically attached to the scandium(III) center in a σ(2)‐fashion. All compounds have been characterized by multinuclear, including (45)Sc NMR spectroscopy. Quantum chemical calculations of these intensely colored arene complexes confirm scandium to be in the oxidation state +3. The intense absorptions observed in the UV/Vis spectra are due to ligand‐to‐metal charge transfers. Whereas nitriles underwent C−C coupling reaction with the reduced arene ligand, the reaction with one equivalent of [NEt(3)H][BPh(4)] led to the mono‐protonation of the reduced arene ligand.