Kinetics of nucleophilic attack on co-ordinated organic moieties. Part 5. Mechanisms of addition of heterocyclic aromatic species to tricarbonyl(1–5-η-cyclohexadienyl)-iron and -ruthenium cations
- 1 January 1977
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in J. Chem. Soc., Dalton Trans.
- No. 6,p. 574-578
- https://doi.org/10.1039/dt9770000574
Abstract
A kinetic investigation has been made of the addition of heterocyclic aromatic molecules to the cations [M(C6H7)( CO)3][BF4](1; M = Fe or Ru). For RH = pyrrole and M = Fe or Ru, the equation Rate =k[complex][RH] is observed, while a similar second-order law holds for RH = furan and M = Fe. These results are consistent with [M(C6H7)(CO)3][BF4]+ RH →[M(C6H7R)(CO)3]+ HBF4(i) electrophilic attack by the dienyl cations on the heterocyclic aromatics. The absence of primary kinetic-isotope effects for RH = pyrrole and M = Fe or Ru shows that the final proton loss is rapid, and suggests that either π- or σ-complex intermediate formation is rate determining. The relative susceptibility of a wide range of heterocyclic aromatic substrates towards the electrophile [Fe(C6H7)(CO)3]+ has been established in both nitromethane and acetonitrile as solvents, showing a difference of 106 between pyrrole and thiophen.Keywords
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