Kinetics and Mechanism of Cyclopropanation of Cyclooctene by [Fe(η5-C5H5)(CO)2CH2SPh2]BF4
摘要:
The kinetics of reaction of [Fe(eta(5)-C5H5)(CO)(2)CH2SPh2]BF4 with cyclooctene in CH2Cl2 solution have been studied under pseudo-first-order conditions at room temperature. The variation of k(obs) is nonlinear in both cyclooctene and added Ph2S. The results are interpreted in terms of a two-step reaction in which the cation [Fe(eta(5)-C5H5)(CO)(2)CH2SPh2](+) undergoes reversible, dissociative loss of Ph2S followed by competitive capture of the methyleneiron complex by cyclooctene to produce bicyclo[6.1.0]nonane. The methyleneiron intermediate is 4-5 times more reactive toward diphenylsulfide than cyclooctene. In the absence of added Ph2S, millimolar solutions of the iron complex react with cyclooctene at room temperature with a half-life of about 36 min to give >85% yields of bicyclo[6.1.0]nonane after 3 h, and it is thus more reactive than the dimethyl- and methylphenylsulfonium salt analogues.