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 (NNfc) are reported. Through the use of (NNfc)ScI(THF)2 as a precursor and potassium graphite (KC8) as a reducing agent, the naphthalene and anthracene complexes [(NNfc)Sc]2(μ-C10H8) and [(NNfc)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 [(NNfc)Sc]2(μ-C14H10) indicated that two different structures are accessible in solution. Reactivity studies showed that the naphthalene complex [(NNfc)Sc]2(μ-C10H8) can be converted to the corresponding anthracene species [(NNfc)Sc]2(μ-C14H10) and that [(NNfc)Sc]2(μ-C10H8) can act as either a reductant or a proton acceptor. The reaction of [(NNfc)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.