Physical Organic Chemistry of Transition Metal Carbene Complexes. 27.† Substituent Effects on the Nucleophilic Substitution of [Aryl(thiomethyl)carbene]pentacarbonylchromium(0) Complexes by Amines in Aqueous Acetonitrile

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