A Scandium Complex Bearing Both Methylidene and Phosphinidene Ligands: Synthesis, Structure, and Reactivity

The scandium complex bearing both methylidene and phosphinidene ligands, [(LSc)₂­(μ₂-CH₂)­(μ₂-PDIPP)] (L = [MeC­(NDIPP)­CHC­(NDIPP)­Me]⁻, DIPP = 2,6-(ⁱPr)₂C₆H₃) (2), has been synthesized, and its reactivity has been investigated. Reaction of scandium methyl phosphide [LSc­(Me)­{P­(H)­DIPP}] with 1 equiv of scandium dimethyl complex [LScMe₂] in toluene at 60 °C provided complex 2 in good yield, and the structure of complex 2 was determined by single-crystal X-ray diffraction. Complex 2 easily undergoes nucleophilic addition reactions with CO₂, CS₂, benzonitrile, and tert-butyl isocyanide. In the above reactions, the unsaturated substrates insert into the Sc–C­(methylidene) bond to give some interesting dianionic ligands while the Sc–P­(phosphinidene) bond remains untouched. The bonding situation of complex 2 was analyzed using DFT methods, indicating a more covalent bond between the scandium ion and the phosphinidene ligand than between the scandium ion and the methyl­idene ligand.