Theoretical Investigation Of Reaction Mechanisms Of Transition Metal Ti~+ And Ni~+ With Methanol And Ethanol

Density functional theory (DFT) has been employed to survey the gas-phase reactions of first-row transition metal ions Ti⁺ with methanol and Ni+ with ethanol. For the reactivity of methanol with Ti⁺(⁴F and ²F) , geometries for all the stationary points involved are fully optimized at the B3LYP/DZVP+6-311+G(2df,2p) and the reaction is analyzed in terms of the topology of potential energy surface. Approach of Ti⁺ towards methanol could form either''classical''O or''nonclassical''η3-methyl-H attached 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 H₂ and H elimination (producing TiOCH₂⁺ and TiOCH₃⁺); and the C-H activation is unlikely to be important. Through the bond insertion -H shift -reductive elimination mechanism, the products of closed-shell molecule (H₂ and methane) elimination could take place on the doublet PES owing to a spin inversion occurring in the course of initial bond insertion; while only the quartet products is produced adiabatically via the simple bond insertion– reductive elimination mechanism for the loss of a radical-type species (H or CH₃). In the reaction of Ni+ with ethanol, geometries and energies for all the stationary points involved are investigated at the B3LYP/6-311++G(d,p) level. Five different"classical"O and"nonclassical"ethyl-H attached isomers are found for the Ni+- ethanol complexes. The classical complexes are much more stable than the nonclassical ones. Extensive conversions could occur readily between these encounter complexes. The product of H₂O and C₂H₄ arises from three reaction pathways, i. e., Ni⁺ insertion into the polar C-O bond and direct H-shift in the classical complexes, C^β-H activation through the nonclassical methyl-H attached complex of Ni⁺- ethanol. Activation of the C^α-H bond of ethanol by Ni+ through the classical complexes leads to the H₂ loss. The theoretical work sheds new light on the title reactions and can be considered as a new approach to the reaction mechanisms of transition metal ions with primary alcohols.