Importance of frontier orbital interactions in addition reaction of water to disilene

Addition mechanisms of water to disilene were investigated in detail using the high level ab initio molecular orbital (MO) theory. We have found that the search for transition states by ab initio MO calculations combined with the frontier MO theory provides a good perspective view of the mechanisms of the reaction of disilenes and water. The initial electrophilic and nucleophilic interactions of the water with disilence give the corresponding weak complexes, C_E and C_N, which leads to the next nucleophilic and electrophilic attack of the water part, respectively. The latter pathway requires an antarafacial approach, while the former pathway proceeds via suprafacial addition. Whereas in the model disilene-water addition reaction, the pathway from C_E is more favorable than the pathway from C_N, the stereochemical ambiguity of the addition reactions found experimentally may be explained by the competition of the two pathways.