Theoretical insights into C–C bond formation through isonitrile insertion into a Cp*Ti complex

Abstract

The migratory insertion of isonitriles into the metal–C bond is important for constructing C–C bonds in organic and pharmaceutical syntheses. We examine the reaction of Cp*(Cl)Ti(diene) with isonitriles using density functional theory calculations. At room temperature, the bis-insertion reaction occurs easily for N-tert-butyl (tBu), methyl (Me), ethyl (Et), 2,6-dimethylphenyl (Ar), and N-1-adamantyl (1-Ad)-substituted isonitriles. The elementary reactions include the isomerisation of Cp*(Cl)Ti(diene), migratory insertion of the first isonitrile into a Ti–C bond, C–C reductive elimination, β-H elimination, migratory insertion of the second isonitrile into a Ti–H bond, and C–C reductive coupling. Two reliable fragmentation mechanisms are suggested for the bis-insertion products. For the bulkier tBuNC, ArNC, and 1-AdNC, the β-H elimination reaction pathway is dominant. For the smaller MeNC and EtNC, the γ-H elimination reaction pathway competes with the β-H elimination. For ArNC, the isomerisation reaction pathway to a newly predicted “σ complex” is kinetically favourable.