Understanding selectivity in the oxidative addition of the carbon-sulfur bonds of 2-cyanothiophene to Pt(0)

The reaction of 2-cyanothiophene with a zerovalent platinum bisalkylphosphine fragment yields two thiaplatinacycles derived from the cleavage of the substituted and unsubstituted C-S bonds. While cleavage away from the cyano group is preferred kinetically, cleavage adjacent to the cyano group is preferred thermodynamically. Density functional theory using B3LYP level of theory on a model of this system is consistent with experimental results in that the transition state energy leading to the formation of the kinetically favored C-S bond cleavage product is lower by 5.3 kcal mol(-1) than the barrier leading to the thermodynamically favored product. There is a 6.7 kcal mol(-1) difference between these two products. The cyano substituent at the 2-position of thiophene did not substantially change the mechanism involved in the C-S bond cleavage of thiophene previously reported.