Unprecedented flexibility of the >TiSi< group for the addition of H2

Abstract

We show using DFT calculations that a coordinatively unsaturated >TiSi< group exhibits an unprecedented flexibility for the reversible addition of dihydrogen. The H₂ attachment may lead to a variety of hydrogenated species (near-equivalent in energy), which contain three–center Ti⋯H⋯Si and terminal Ti–H and Si–H bonds. The >TiSi< moiety also exhibits a particularly low electronic barrier for heterolytic H₂ attachment (∼0.0 eV) and beneficial thermodynamics of this process. One important path leads to the kinetically preferred H–Ti⋯H⋯Si isomer (at −0.5 eV with respect to the substrates, denoted II), which is capable of a subsequent low-barrier H₂ release. Chemically pre–engineered compounds containing the >TiSi< grouping might be used for efficient H₂ transfer catalysis in organic and inorganic hydrogenations, and for charging/discharging of the hydrogen storage materials.