Scandium Arene Inverted-Sandwich Complexes Supported by a Ferrocene Diamide Ligand

The synthesis and characterization of the first scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand (NN^fc) are reported. Through the use of (NN^fc)ScI(THF)₂ as a precursor and potassium graphite (KC₈) as a reducing agent, the naphthalene and anthracene complexes [(NN^fc)Sc]₂(μ-C₁₀H₈) and [(NN^fc)Sc]₂(μ-C₁₄H₁₀), respectively, were synthesized and isolated in moderate to high yields. Both molecular structures feature an inverted-sandwich geometry and exhibit short Fe–Sc distances. DFT calculations were employed to gain understanding of the electronic structures of these new scandium arene complexes. A variable-temperature NMR spectroscopic study of [(NN^fc)Sc]₂(μ-C₁₄H₁₀) indicated that two different structures are accessible in solution. Reactivity studies showed that the naphthalene complex [(NN^fc)Sc]₂(μ-C₁₀H₈) can be converted to the corresponding anthracene species [(NN^fc)Sc]₂(μ-C₁₄H₁₀) and that [(NN^fc)Sc]₂(μ-C₁₀H₈) can act as either a reductant or a proton acceptor. The reaction of [(NN^fc)Sc]₂(μ-C₁₀H₈) with excess pyridine led to a rare example of C–C bond formation between two pyridine rings at the para position.