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

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 CH3 I 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 CH3 I. 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 (C2 H6 ) 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 CH3 I is mediated by Au atoms via [(CH3 )2 -Au-I2 ] as an intermediate.