Theoretical survey of the potential energy surface of Ti+ + methanol reaction

The gas-phase reaction of Ti(+) ((4)F and (2)F) with methanol is investigated using density functional theory. Geometries and energies of the reactants, intermediates, and products involved are calculated. The approach of Ti(+) toward methanol could form either a "classical" O- or a "nonclassical" eta(3)-methyl H-attached complex. The reaction products observed in the experiment (Guo, Kerns, Castleman J. Phys. Chem. 1992, 96, 4879) are produced via the classical association rather than the nonclassical complex. All possible pathways starting with C-O, C-H, and O-H activation are searched. Methane and methyl loss products (TiO(+) and TiOH(+)) are produced via the C-O activation; the O-H activation accounts for the H(2) and H elimination (producing TiOCH(2)(+) and TiOCH(3)(+)); and the C-H activation is unlikely to be important. Through the bond insertion (H shift) reductive elimination mechanism, the products of a closed-shell molecule (H(2) or methane) elimination could take place on both the quartet and doublet PESs owing to a spin inversion occurring in the course of initial bond insertion, whereas only the quartet products are produced adiabatically via the simple bond insertion-reductive elimination mechanism for the loss of a radical-type species (H or CH(3)). The computational results are in concert with the available experimental information and add new insight into the details of the individual elementary steps.