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.