Claude F. Bernasconi and, S. Bhattacharya
Feb 21, 2003
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0
Influential Citations
9
Citations
Journal
Organometallics
Abstract
A kinetic study of the reactions of (CO)5CrC(SMe)C6H4Z (Z = 4-CF3, 4-Cl, 4-F, 4-Me, 4-MeO, and 4-Me2N) with n-butylamine, 2-chloroethylamine, piperidine, and 1-(2-hydroxyethyl)piperazine in 50% MeCN−50% water (v/v) at 25 °C is reported. In all cases the nucleophilic attachment of the amine to the carbene complex is rate limiting, which contrasts with the previously reported aminolysis of the methoxy analogues ((CO)5CrC(OMe)C6H4Z), where leaving group departure is rate limiting in most cases. The substituent effect on the nucleophilic attachment step is much weaker (average ρ = 0.55) than for the methoxy analogue (ρ = 2.03). It is shown that the small ρ value for (CO)5CrC(SMe)C6H4Z is “normal” and reflects the near cancellation of the substituent effects on the partial positive and partial negative charges at the transition state. These findings provide evidence that the high ρ value for (CO)5CrC(OMe)C6H4Z is “abnormal” and the result of the strong π-donor effect of the methoxy group on the reactant carben...