Reduced Arene Complexes of Scandium

Abstract

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=C6H3-3,5-Me2) to give scandium complexes [M(thf)n][Sc{N(tBu)Xy}2(RA)] (M=Li–K; n=1–6; RA=C10H82− (3-Naph-K) and C14H102− (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 σ2:π-coordination mode, whereas the anthracene dianion is symmetrically attached to the scandium(III) center in a σ2-fashion. All compounds have been characterized by multinuclear, including 45Sc 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 [NEt3H][BPh4] led to the mono-protonation of the reduced arene ligand.