Photoassisted Homocoupling of Methyl Iodide Mediated by Atomic Gold in Low-Temperature Neon Matrix.

Abstract

Infrared spectroscopy and density functional theory calculations showed that the gold complexes [CH3-Au-I] and [(CH3)2-Au-I2], in which one and two CH3I molecule(s), respectively, are oxidatively adsorbed on the Au atoms, are formed in a solid neon matrix via reactions between laser-ablated gold atoms and CH3I. Global reaction route mapping calculations revealed that the heights of the activation barriers for the sequential oxidative additions to produce [CH3-Au-I] and [(CH3)2-Au-I2] are 0.53 and 1.00 eV, respectively, suggesting that the reactions proceed via electronically excited states. The reductive elimination of ethane (C2H6) from [(CH3)2-Au-I2] leaving AuI2 was hindered by an activation barrier as high as 1.22 eV but was induced by visible-light irradiation on [(CH3)2-Au-I2]. These results demonstrate that photoassisted homocoupling of CH3I is mediated by Au atoms via [(CH3)2-Au-I2] as an intermediate.