Abstraction of the I Atom from CH₃I by Gas-Phase Au _n ^- (n = 1-4) via Reductive Activation of the C-I Bond.

ABSTRACT: Gas-phase reactions of atomic gold anions and small gold cluster anions, Au _n ^- (n = 1-4), with CH₃I were investigated to clarify the effect of the cluster size on C-I bond activation and to elucidate the key properties of Au clusters that govern the reactivity. Au _n I^- identified by mass spectrometry was observed as a common reaction product. Photoelectron spectroscopy and density functional theory calculations revealed that Au₂I^- has a linear structure in which the I atom is bonded to Au₂, and Au₃I^- and Au₄I^- take a two-dimensional structure in which the I atom is bonded to triangular Au₃ moieties. Pseudo-first-order kinetic analyses of the reaction revealed the inverse correlation of the reactivity of Au _n ^- toward CH₃I and the electron affinity of Au _n , indicating the reductive activation of the C-I bond. Especially, Au₂ ^- showed the highest reactivity to form Au₂I^- as the main product, whereas the adduct compound Au₂CH₃I^- was hardly formed, in sharp contrast to the reaction of Au^- reported previously. On the basis of theoretical calculations, we propose that the reaction proceeded dominantly via the I atom abstraction pathway (attack of Au₂ ^- from the I atom side), which is highly preferential from the viewpoint of both the energetics and a steric factor. This study demonstrates that not only the reactivity but also the reaction mechanisms and products are governed by the cluster size in C-I bond activation by Au clusters at the smallest size region.

SUBMITTER: Muramatsu S 

PROVIDER: S-EPMC6643549 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature