Adsorption mechanisms of isoxazole and oxazole on Si(100)-2 × 1 surface: Si-N dative bond addition vs. [4+2] cycloaddition

The surface reaction pathways of isoxazole and oxazole on Si(100)-2 1 surface were theoretically investigated. They both form a weakly bound Si-N dative bond adduct on Si(100)-2 1 surface. In the case of isoxazole, the barrierlessly formed Si-N adduct is the most important surface product, that cannot be easily converted into other species. On the other hand, a facile concerted 42 _CC cycloaddition without involving the initial Si-N dative bond adduct was also found in the case of oxazole adsorption. The existence of Diels-Alder reactions is attributed to the particular arrangement of the two heteroatoms of oxazole in such a way that the two Si-C -bonds can be formed in a 42 fashion. In short, the unique geometric arrangements and electronegativity of these similar heteroatomic molecules yielded distinctively different surface reaction characteristics.