Reduction Chemistry of Bis(cyclopentadienyl) Scandium Iodides with Isocyanides: Sc(II) Complexes, Isocyanide Coupling, and Aquo Adducts

Abstract

To better define scandium(II) reduction chemistry and to study ligand effects on the hyperfine coupling to ⁴⁵Sc in the EPR spectra of Sc(II) complexes, which could be useful in the design of qubits based on nd¹ electronic configurations, the reduction of bis(cyclopentadienyl) scandium(III) iodide complexes in the presence of isocyanide ligands has been examined. Both pentamethyl- and tetramethylcyclopentadienyl complexes have been examined with isocyanides CNR, where R = 2,6-dimethylphenyl (Xylyl), 1-naphthyl (Naph), and 2,6-diisopropylphenyl (Dipp). The synthesis and structures of the isocyanide adducts of Sc(III) metallocene iodides, Cp^x₂ScI(CNR) [Cp^x = C₅Me₅ (Cp*) and C₅Me₄H (Cp^tet)] are described as well as EPR data on the Sc(II) products formed by reduction of Cp^x₂ScI in the presence of CNR. A more direct synthetic route to the Sc(II) complex, Cp*₂Sc(CNXylyl)₂, is reported. New Sc(III) complexes obtained from these reactions are also described including [Cp^tet₂Sc(μ-CN)]₄ which is the first crystallographically characterized Sc complex containing (CN)^1– cyanide ligands, as well as products with two and three coupled isocyanides, Cp^tet₂Sc(XylylNCCNXylyl)ScCp^tet₂, Cp^tet₂Sc(C₂₇N₃H₂₈), and Cp^x₂Sc(C₃₃N₃H₂₂). In addition, the [Cp*₂Sc(CNXylyl)₂]¹⁺ cation was isolated as the (BPh₄)^1– salt for comparison with the Sc(II) analog, Cp*₂Sc(CNXylyl)₂, and the unexpected organometallic aquo adducts, [Cp^tet₂Sc(H₂O)₂][I][THF] and Cp^tet₂Sc(OH)(H₂O), were fortuitously crystallized.