STRUCTURES AND ENERGIES OF INTERMEDIATES IN THE REACTIONS OF SINGLET OXYGEN WITH ORGANIC PHOSPHINES AND SULFIDES

Structures, energies, and vibrational frequencies of various intermedi ates and transition states in the reaction between phosphines and sing let oxygen have been calculated using ab initio methods, including RHF , MP2, and CASSCF optimizations, and energy evaluations using various basis sets including electron correlation. A surprising result is that the only intermediate located for the first step of the reaction has the cyclic phosphadioxirane structure. An acyclic intermediate is not stable. This result contrasts strongly with the reaction of sulfides, where both cyclic and open structures are stable. Improved calculation s for thiadioxirane and peroxy sulfoxide are reported. Transition stru ctures leading to the phosphadioxirane intermediate and its reactions with water and phosphines have also been examined, as has the rotation al barrier of the intermediate.