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.