Reaction mechanisms of dissociative chemisorption of HI, I2, and CH3I on a magic cluster Al 13− (original) (raw)

We have investigated the transition-state structures and reaction mechanisms for the dissociative chemisorption reactions of HI, I 2 , and CH 3 I on the magic cluster Al À 13. The HI, I 2 , and CH 3 I molecules approach Al À 13 with an end-on orientation rather than a side-on orientation because of the more effective orbital overlap in the end-on orientation. The reactions of Al À 13 with HI and I 2 would produce Al 13 HIand Al 13 I 2 2 , respectively, because of large exothermic energy changes and relatively small activation energies. The reaction of Al À 13 with CH 3 I is unlikely to take place because of the low mobility of CH 3 on Al À 13 and the high activation barrier for the S N 2-type reaction. The dissociative chemisorption reactions are preferred thermodynamically to the abstractive chemisorption reactions.