Gas-Phase Transition Metal Ion Chemistry: The Reactivity and Specificity of Atomic Iron(I), Chromium(I), and Molybdenum(I) Ions with Alcohols

The reactions of gas-phase atomic transition-metal ions Fe⁺, Cr⁺ and Mo⁺, generated by multiphoton dissociation ionization (MPD/MPI), with a series of aliphatic alcohols were studied by using Fourier transform mass spectrometry. The concepts of reactivity and specificity are used to correlate the different insertion reaction chemistry of each metal ion. These metal ions undergo three classes of bond insertion reactions: C—O insertion (dehydration), C—H or O—H insertion (dehydrogenation), and C—C insertion. The total reactivity of each metal ion is a function of its electronic configuration and the aliphatic chain length and degree of branching of the alcohols. For straight-chain alcohols containing three carbons or more, the order of reactivity is Fe⁺ > Mo⁺ > Cr⁺. For shorter alcohols Mo⁺is the most reactive species while Cr⁺ is unreactive with methanol and ethanol.